well i just had this problem. there was this book i really wanted to read but i couldn't even find it in the library!!! i was pissed to say the least of course. i have found one site though that actually has tons of books.
abebooks. com actually has books that are already out of print and the really famous books too. you can even sell books there. not only that, i found out that if you bought books from there, some participating booksellers actually sent them to you with the shipping for free.
i'm thinking of getting some and have put the link up if you guys are interested. it's not only storybooks they're specialised in, like i said earlier, it can be used too, even textbooks. best of luck to you guys in getting the books of your choice.