Well...you mean there are books *other* than HP??
Sarcasm mode OFF. I love books, and I'll read basically anything (except cheesy romance). A few stand out as my favorites, though...
Ender's Game, and all the sequels, by Orson Scott Card: You've got to read these books! Especially if you're young, that's the best time to read them (although they're essentially adult novels, the theme is to some extent directed at intelligent children). Socially, they remind me a lot of Harry Potter, minus the magic. They're real page-turners and very easy to read, but will make you think.
The Outsiders by S.E. Hinton: I read this book in seventh grade, and although it is clearly on a seventh-grade reading level (if that), it still has a special place in my heart. I believe that no one should be allowed to graduate from middle school without reading this book, because it communicates the importance of tolerance better than any other work I've ever read. It's a simple, short story, but if it doesn't make you cry, you have no soul.
1984 by George Orwell and Brave New World by Adolphus Huxley: These books are together because they are essentially the same and yet very, very different, each uniquely compelling and frightening. They're a little harder to read, especially 1984, but both are awesome.
Anything by Garth Nix: Because he's one of the best modern storytellers out there (with the possible exception of Ms. Rowling herself!).
Anything by Isaac Asimov: Because he's possibly *the* best science fiction writer who ever lived. Just read him.
Anthem by Ayn Rand: This book is much shorter and easier to read than The Fountainhead (see below), and I'd recommend it if you're not familiar with Objectivism; it's a good introduction and is a great story, too.
EDITED, because I forgot The Lord of the Rings by Tolkein: How, how, how I could forget these wonderful books, I haven't a clue. Before the Potter-Loving-Era in my life began, they were my only exception to the no-fantasy rule. The writing style is a tad more difficult that HP, but nothing too bad. They're exciting stories and there's oodles of symbolism, too.
And now, my two absolute favorite books of all time... (and, yes, I love them even more than HP!)
Les Miserables by Victor Hugo: Very hard book, and very, very long. I adore it. All 1463 pages of it. I've read and re-read this book since age fourteen, have bookmarked, highlighted and cried over it more times than I can count. Enjolras is my idol and I sing the musical's soundtrack almost daily. No words can describe its awesome-ness, except possibly these: Read it!
The Fountainhead by Ayn Rand: This book is my personal meaning of life, with some suppliment from Les Miserables. It has taught me to be proud of myself and to be independent. Every ounce of self-esteem I have was found within its pages (because heaven knows I had none when I first picked it up!). It's the most difficult book I've ever read, but also the most rewarding.
Yeah, those are a few (emphasis on a FEW) of my favorites. Anything mentioned above is well worth your time.
Oh...and Harry Potter, of course! (Order of the Phoenix is by far my favorite!)