Ah, yes---I read The Wizard of Oz. Granted, it was years ago, but it still counts, no?

But on the REAL question::: I've never been a fan of picking just one, so deal with it.

---The Abhorsen Trilogy, by Garth Nix. Whoa:::this completely blew my mind, especially the first one, Sabriel. His world is amazing, as ar the characters, the plot, the "bell" system....*sigh* Genius
---The Kingdom of Thorn and Bone (So far, just The Briar King and The Charnel Prince), by Gerg Keyes::: Equally amazing, although still unfinished. I'm most confident that will go down as one of the greatet fantasy series of all time.
---As much as I doubt this needs to be said, I'll go ahead and say it anyways---A Song of Ice and Fire, by George R. R. Martin. Just read.
---The Perilous Gard, by Elizabeth Marie Pope:::What can I say? I'm a sucker for any retelling of Tam Lin (except Fire and Hemlock. Yuck.) The author only wrote two books, but this is far better than the other, in my opinion.
---Feist. More specifically, The Serpentwar Saga, as I haven't read anything else by him---YET. And that's always a good thing.
---Anything by Patricia A. McKilip. You don't even need to read her books for the plot, or characters, or her wonderful settings---the language itself is enough. It's absolutely beautiful, and captures the fairytale feeling like none I've ever read before.

Ah, magic does exist.