Trying to plan my ability trees and stats, including points received from books and any other source I don't know, how many points can be obtained without modding the game?
150/154* attribute points and 51/53 talent points:
The Black Emporium DLC includes the following:
I asterisked the number because you can gain additional attribute points and talent points from the following:
Nothing of note.
The "hard" level cap might be 50, but a normal play through won't go anywhere near that. Expect to finish at level ~22/23. To be safe, let us assume level 22. That means 21*3 for 63 attribute points from leveling, and 21 ability points from leveling. Anything beyond that is gravy.
Mark Trapp correctly lists the availability of bought items to increase stats. So, add points as appropriate to your game.
However, he neglects a quests which can also reward the player with more attribute and (less commonly) ability points. I think you get earn 6-8 more attributes, but I only one additional ability point.