I need help progressing Act 4.

Hey so I just used the Memory of Memories to get into the room with the diary about using Wishcraft and talked to Loop about it. They told me to keep looking for more books I can read with the Memory. I tried to book in the secret library but it told me the words were too complex for Siffrin to understand. Please help, I have tried to go in blind until now, but I have genuinely looked through almost every room in the House twice and am going insane (fitting for the story I guess).

PS: This is barely relevant and I don't want anyone to spoil if I'm right or wrong about this, but my crack theory is that Siffrin wrote the diary and Loop is the clone that they made with Wishcraft. This is why Loop knows so much about Siffrin but not much about the King or timeloops or anything. The only purpose of this post script is as record of either my foolishness or brilliance for a few days from now when I finish the game.