Well, there are the Nathaniel Fludd books, but I haven't read any of those. They look very simple, but very good. They're about a boy who studies magical creatures, I think. I don't plan to read them any time soon, though; they look good, but I'd probably read them so quickly that there just wouldn't be much point in checking them out. There's also a series called Lowthar's Blade, though I haven't read it, either; it's medieval fantasy. There's also a book called Werewolf Rising, which I haven't read yet but plan to, and one called The Falconmaster, a historical fantasy that's out of print but still available in some libraries, including mine; I've read it, and it's great! I prefer the Theo books, though.