Very cool concept!
It took me a while to understand how to choose the proper knowledge to give humanity. Lost 4 times but finally beat one of the prophecies on my 5th try.
I'd suggest making it a requirement to read the prophecy first before letting the player choose books or give knowledge. A simple message on the screen saying "The prophecy... I should read it" and making the prophecy slab glow or something like that should work.
Good work!