if you have not activated all 3 words of the bend will shout the quest will not start .......watch the end of the video ..... At the Summit of Apocrypha part 1 https://youtu.be/v8rqt3IXTcQ
hopes it helps
BTW ........if it works here is the complete walk through if you get stuck again ..........all book puzzles solved
Part 2 https://youtu.be/6lGgf4n38Pw
Part 3 https://youtu.be/ANp00jDxV6Y
Part 4 Final battle https://youtu.be/FKTxwBy7OL0
PS ...........good luck
The only thing I can think of is this:
Use the console to drop both books separately.
Do a quick save.
Pick up one book.
If nothing happens reload and pick up the other book.