Overview:
This tiny, esp-free mod simply automatically uses skill books once they are added to the player's inventory if the "Grab" key is not held when the book is added, and the player's relevant skill is lower than 100.

If you want to change the upper-cap on when the skill books stop getting used, simply change < 100 in this line to < 69 or whatever
if rOwner.GetPermanentActorValue (GetBookSkill rBase) < 100 && isControlPressed 27 == 0 && GetType rBase == 25

Requirements:
JIP LN, xNVSE, Johnny, the usual stuff.
ShowOffNVSE

Installation:
Regular installation.
Please endorse and vote if you appreciate the mod.

Compatibility:
Should be compatible with any book that uses the book form type (25).

Limitations:
The automatic use doesn't trigger if the book is added during a container menu/barter until 1/4 of a second after leaving the menu. This could actually be changed to occur in menus as well, but I actually prefer it this way so that books can be moved around in inventories and such without triggering the automatic use. Simply change the line
callafterseconds 0.25 ({} => rOwner.EquipItem2 rBase)
in the text file to 
callafterseconds 0.25 ({} => rOwner.EquipItem2 rBase) 1
and re-save the text file to change it to happen during menus as well.

Permissions:
Do whatever.

Support:
If you'd like to support my modding work or say thanks, feel free to donate via the Nexus or here at Ko-Fi.