It is always helpful to know what books you have read that you particularly liked. Often the things you loved in a piece of one genre are also present in a work of a completely different genre. I began reading The Lord of the Rings in sixth grade and have read it many times since, but nothing else in the fantasy genre has ever floated my boat. Tolkien possessed a vast knowledge of mythologies and literatures from many countries and ages (they crop up everywhere as the breadth of your reading expands), and he was a master of the writing craft--pacing, timing, dialog, suspense, comic relief, imagery, lyricism. Though many of my teachers (even in college) cringed at Tolkien's hold on the literary tastes of students, The Lord of the Rings really cranked up the reading level of a lot of us. I think Harry Potter has played a similar role--I wonder if there has been an uptick in Dickens' readership (from Beedle the Bard to Beadle Bumble). If teachers aren't working that angle, they should be!
Books that you will likely be required to read sooner or later include To Kill a Mockingbird, Catcher in the Rye, Of Mice and Men, Lord of the Flies--all gorgeous stories that it doesn't hurt to read for pleasure, plus you'll have a great advantage when you have to read them again with all the baggage of homework attached. Great, but anthologized to death, are The House on Mango Street, I Know Why the Caged Bird Sings, and The Joy Luck Club.
Jerry Spinelli has some great books. Island of the Blue Dolphin is always good, or Julie of the Wolves. Also, A Farewell to Manzanar or The Summer of My German Soldier. You might also try a western (Hondo by L'Amour is good) or scifi (Fahrenheidt 451 by Bradbury) or mystery (And Then There Were None by Christie). If you've never read Tom Sawyer, go for it. The Pandora books, based on the mixed mythology of Pandora and the seven deadly sins, are fun.