Percival and Jill/Eustace fail to see the obvious: Percival doesn't realize he's found the grail and the other two don't realize they've reached one of the signs (the "Under Me.") Their quests are also faith-based. This is obvious on Percival's part, but Jill and Eustace have to go off of a very small bit of info, then put their trust in Aslan to do the rest.
. . . and that's it. I picked up a couple of books from Barnes and Noble's "Discover Great New Authors" section. It's a great place to find uniqueness. I have another book to read first, but hopefully I'll be getting to the new ones soon (especially since one is about Charlotte Bronte . . . . )