Question

Hello Rabbi, regarding the last chapter in the series on the Holy One, blessed be He, and the world about divine knowledge and free choice: we were taught back in high school that the fact that God knows does not mean we have no choice. In other words, He knew what we would choose, and that is not dependent on the choice itself. It’s like having a letter that you open at the end of the day and seeing that it knew what you did all day, even though you had completely free choice. As for how it is possible to know something that has not yet happened, I could, with some difficulty, explain it by saying that perhaps He can “calculate,” or know, what a person’s heart inclines toward, and therefore He would know what he will choose anyway.
My question is: why must His knowledge necessarily prevent free choice? It’s like the story the Rabbi brought about the book that knows everything. The person who read it had completely free choice, which ultimately brought him to his death, and that does not necessarily have anything to do with opening the book, or with what the book did or did not know. I didn’t fully understand why this is a contradiction.
Thank you