Disclaimer: This mod has not been heavily tested, yet. So some things may be unbalanced. Let me now if they are or not. Users should make a hard save before installing this mod and should be ready to use the respec option (either from mod or the base game option) to revert some of the change brought by this mod or to account for future update.
Also, respect to the base material wasn't always the focus of this mod, rather I tried to make the Feat and Abilities added as balanced as I could for the game.

SOURCES : The Lost Grimoire on github (this should have been here at release but I forgot)

Install Instruction:
1. Download and install Unity Mod Manager
2. Download the mod
3. Extract the mod archive and put the mod folder in the "Mods" folder of the Game (\Steam\steamapps\common\Pathfinder Kingmaker\Mods).
4. Play the game and Enjoy.

Archetype:

• SpellBinder: Does not include the possibility to switch wich spell are selected at level 4 and higher, because it would be a hassle to do and I'm lazy but also Sorcerer can't change their spell and that would be unfair and unbalanced to allow wizard to do it. This archetype is compatible with Scroll Savant and Thassilonian specialist (it is chosen on the arcane bond selection).
• Poleiheira Adherent: Big change for this archetype from pnp. Mount just allow the wizard to delay the next time they must rest by a certain number of hours. Master Mariner is replaced by Great Traveler  that increase the travel speed on global map by 30%(number to adjust depending on your input). This archetype is compatible with Scroll Savant. It is chosen on school selection.
  

Focused Arcanes School (subschool)

• Enhancement (Transmutation)
• Prophecy (Divination)
• Counter-Spell (Abjuration) : Counter Spell Mastery is a free action, as you need your swift action to do the counterspell on your adversary turn.
• Teleportation (conjuration)
• Phantasm (Illusion): The Terror ability don't let you choose which ally will make the Attack or Opportunity, but will choose the one with the highest attack bonus
• Life (necromancy) : The healing grace has been adapted. You can heal/damage any target that has been targeted by one of your spell. The healing will be done after a spell is cast when : 1) You use the Ability to do so choosing the first target; 2) You cast another spell ; 3) After 2 round.   If you don't use the ability yourself (case 2 and 3), the base target will be chosen automatically between all the valid target depending on they're current damage or hp left so that the target is always the one on which the ability would have been the most helpful.  In any case if after affecting the first target there is some overheal or overdamage it will be affecting another valid target automatically (so that nothing is wasted).
• Admixture (Evocation) : the level 8 power (elemental manipulation) had many hurdles that needed to be overcome to be done properly. I'm kind of lazy and no solution would have been ideal so I revamped the power as such: It create a zone where every allies of the Wizard see their elemental spell changed to another element chosen by the Wizard. It is like the 1st level power but for the whole group. 
  

Arcane Discoveries:

• Alchemical Affinity: Does not include the last part of the feat about copying spell from formula book, because it make no sense in the game.
• Forest Blessing
• Feral Speech: Adapted for the game as an ability that allow to make persuasion check to try to charm or even dominate animal (and later on Vermin)
• Golem Constructor : Adapted for the game as a pet, see Golem Companion, below
• Idealize
• Immortality: Allow to ignore penalty from the Amulet of Dying Wisdom and the Older Hero feat (see below)
• Knowledge is Power
• Opposition Research : A new implementation of this feat, that will be available alongside the one from eldritch arcana. This feat doesn't work for Thassilonian Specialist by design.
• Resilient Illusions
• Staff-Like Wand : If you use the Craft Magic Item mod then the prerequisite should be Craft Wand, if not it will be Skill Focus(UMD)
• Split Slot : you can only take it once for now (working on a clean way to make it as per pnp)
• Steward of the Great Beyond : Do not counter teleportation, because I fear it could mess with script in combat and all that sort of thing
  

New Spell:

All that follow is my personal attempt at making the divination school more attractive:

• Greater True Strike : Homebrew, like true strike but you can cast iton another creature and the bonus can be split between multiple attacks
• Clairvoyance : Create an area that reveal the fog of war and allow tosee creature, works anywhere on a map. Be careful, in some circumstance, if you make an aggressive action against the revealed creature combat may start when neither them or you can actually attack (for example if they are in a room with a closed door) but the fight should end after a few round.
• Heighten Awareness : mostly like pnp but with better bonus to make it better
• Discern Enemies Location : Adaptation of Discnern Location, this spell will place a map marker on enemies that fail a will save, than you can see them on the map even if they are in the fog of war. 
• Unbound Sight : Adaptation of Insect Spies (more or less), it extendthe radius at which hidden item and trap can be detected by the caster. The greater version can be casted on another creature. 
• Contact Other Plane : Launch a book event that allow you to ask some basic question to receive a buff on one Knowledge skill until the next rest or obtain some information about the area where you are : Reveal Information about the enemies (like when doing knowledge check) for when you inspect them, Reveal some trap in the area or reveal some hidden object in your area. All the three last option actually use your caster level and Intelligence Modifier when deciding what to reveal.
  Note: I'm not a native English speaker AND have dyslexia, so... I tried to write some nice text for this spell but I bet there are many spelling mistake, grammar horrors and typos. Don't hesitate to report them :)
  
• Lesser Counterspell(lvl1):  This spell allows the caster to see glimpses of the future, immediately learning what spell their target will cast, if any, before the start of their next round.
  Once the caster learn the nature of this spell, they automatically spend a standard action to prepare a counterspell and start accumulating magical energy to disrupt the future spell. Then, when the target finally cast their spell, the caster release their counterspell as an immediate action and must make a Caster level check against a DC equal to 11+ the spell level + the target caster level.If the check is successful, the target's spell is blocked and wasted.

• Counterspell(lvl4): As per Lesser counterspell but with +2 on the CL check
• Greater Counterspell(lvl7) :As per lesser counterspell but with +5 on the CL check
  

Change from Pnp for counterspell: I feel like counter spell per pnp would be tedious (checking which spell is cast), allowing to counterspell by preparing the right spell would be a pain to do. So I opted for a rule that is half way between the normal rule and counterspell with dispel magic. To balanced a bit, the counterspells are effectively fullround action to cast and the Cl check is a bit harder than with dispel (but see Improved counterspell).
Also the spells are of the Divination school. Odd, I know, but: I hope the wording of the spell make it clear how it could be a divination spell and divination sure need some love and some mean to be more useful, I think (I mean, who ever played a diviner? tell me in the comment). That last bit is a first step on my goal to enhance a bit the divination school.

New Feat

• Older Hero : Allow you to make an older character as per pnp rules, except it's a feat(For balance reason: warrior will never take this option and it is really advantageous for caster).The amulet of dying wisdom have been modified to not stack with this feat.
• Improved Counterspell : When you use one of the counterspells, if the targeted spell level is inferior to the counterspell's, no caster level check is required.
  

Golem Companion
This is the part of the mod that is heavily adapted and depart from the pnp rule:

• You don't have to build the golem: selecting the feat give you a permanent pet, like animal companion. The construct companion gain ability and power as they gain level (Gaining Strength, Ac, DR, Attack and Saves Bonus, and Also the spell immunity at higher level).
• The construct don't have their pnp spell vulnerability/advantage (special effects that happen when specific spell are casted at them). It is again for balance reason: the AI wouldn't know how to use the vulnerability so it would only be an advantage for the wizard and be a bit much to powerful in certain case.
• The pet level is tied to your wizard level
• The pet upgrade like animal companion, but at level 11
• I tried to follow pnp rule when I could for the construct stats but often deviated from it for balance reason (A level 9 wizard with a by pnp rule Steam Dragon would be op).
• This pet is not intended to be as strong as an Animal companion, it's intended to be a nice help but nothing more. I'm not sure that this goal have been achieved, I couldn't test all the construct companion options for all the level range.
  
  
  

For now there is only five pet option:

• Ice Golem
• Mud Golem
• Steam Dragon (It's in fact the clockwork dragon but clockworks couldn't be done using base game asset)
• Stone Golem
• Scarecrow
  

All the construct can't be healed using the normal spell and can't be resurrected (you have to rest for that). So Taking the feat add an ability named "Patch Construct" to the wizard that allow to heal the construct 3 time day at a cost of 2 diamond dust.

It isn't much and is costly, so there are also new spell to heal and  improve your golem :

• Make whole: Lvl 2, Restore a bit of Hp to the golem
• Make whole greater: Lvl 4, Restore more hp to the golem
• Rapid Repair: lvl 5, The golem Gain Fast Healing (5) for a short time
• Unbreakable Construct: Lvl 5, The golem gain a bonus Dr of 5/Adamantine that stacks with its existing DR
• Code Skill :lvl 3, The golem gain bonus in Athletics, Mobility, Perception equal to its level, If it already has rank in the skill it instead gain the skill as a class skill.
• Program Feat:lvl 5, The golem gain some feats depending on your choice, the option are: Attack (Gain weapon focus and Improved critical for all its primary weapon), Resistance (Toughness, Lightning Reflex, Great Fortitude, Iron Will), Cooperation (Precise Strike and Outflank)
  

Future possible balance tweak:
As I said, I don't really know how well this feat is balanced, so future option to fix OP companion are in consideration if the comments of the  mod tell me it is unbalanced. Here are the option for now:

• Adjusting the Companion Stats and Ability
• Making the Construct not resurrecting on rest and Adding an ability to do it manually (costing diamond dust)
• Making the construct not act on the master death
• Scraping the spell immunity altogether (if it is the cause of the balance problem)
  

Bugs Fix

• Added the Force descriptor to Magic Missile and Battering Blast
• Added the Polymorph descriptor to Baleful Polymorph
  

Known Bug:

• Fixed in latest version(0.6.3+) : Casting spell from item other than wand wouldn't work.
• Golem can become fatigued and deseased (will fix in next version)
  

Future Plans:
More Arcane Discoveries:

• Ioun Bond : long term project, I'll see if the mod works well first. But it would add Ioun Stones to the game.
• True Name: also a long term project
• Infectious Charm (not working for now)
• Undead Master with the undead pet option
• At least one focused school per arcane school
• Some Elemental school
• Archetype : Arcane Physician (maybe)
• New spell : those needed to do the elemental School and some more divination
  

More Spells, maybe, and feat (don't hesitate to suggest some). At one point I may also do one or two new wizard Archetype.
Also at one point I'll add the mod content to some npc (when it make sense and don't require new AI tweak).

What I won't Do:

• Command Undead (I've other plan for necromancer)
• Lichdom
• Simulacrum, Gate, Planar Binding or other complicated spell that would change the game to much or would be op in the game
• All things non related to wizard
• Werewolf Shape & Multimorph : those feat have no use in the game
  

CREDITS AND THANKS

• To Elmindra and joostjasper for ELdritch Arcana mod: this mod use EA as its base and I couldn't do it without EA.
• To Redjordan for the Advanced Martial Art mod: I borrowed some bit of code from this mod (especially the animal ally feat line code was used as the base for the golem companion)
• To Holic92: I borrowed some tiny bit of their fix to EA and their advice were a great help
• To SpaceHamster : Without their help this mod wouldn't exist, period. Especially for dealing with modified asset.
• To Hsinyuhcan: for their great help and because without their support I'd never started modding in the first place
• To musu from the discord: the number of bug/problem they reported is over 9000!
• To everyone else on the Kingmaker Discord, you guys are the best.