When you are asked to choose a new spell to research, it shows you a page with, like, 8 spells to choose from. This is the same screen you get when you choose “apprentice” from the information menu.
Did you know that you can turn the page and look at the spells you cannot choose to research yet, but will be able to eventually. To keep it kind of mysterious, those spells are in a cipher of weird characters.
I deciphered the characters a long time ago, and will often check to see if I have certain spells that I want to make sure of, like in a start just recently, I went through my unresearched spells to make sure I had the crusade spell waiting for me.