I assume this game has been abandoned, but I have unlocked book 6 and the final spread of the book is blank. I'm unsure if this is a bug or part of the puzzle, but I'm stuck :/
Edit: ok, it's not a bug, I just unlocked the final book and rolled credits. Seeing that the game was inspired by The Secret of Psalm 46 makes me think that I missed a lot of secrets. I didn't manage to decipher the second or third page of the untitled book, or work out what the numbers in Leoryk's book meant. Hopefully someone will come along one day to give me a hint.