I recommend expanding your horizons beyond the dribble that is J.K. Rowling...

The Sun Also Rises - Ernest Hemingway
The Beach - Alex Garland
The Count of Monte Cristo - Alexandre Dumas
1984 - George Orwell
The Catcher in the Rye - J.D. Salinger
Lord of the Flies - William Gerald Golding
Brave New World - Aldous Huxley
Animal Farm - George Orwell
Slaughterhouse-Five - Kurt Vonnegut
The Great Gatsby - F. Scott Fitzgerald
Farewell To Arms - Ernest Hemingway
The Scarlet Letter - Nathaniel Hawthorne
Of Mice and Men - John Steinbeck
Grapes of Wrath - John Steinbeck
Angela's Ashes - Frank McCourt
The Professor's House - Willa Cather
The Day of the Locust - Nathanael West
Appointment in Samarra - John O'hara
The Age of Innocence - Edith Wharton
The Art of War - Sun Tzu
War and Peace - Leo Tolstoy
Leaves of Grass - Walt Whitman
The Sound and the Fury - William Faulkner
Adventures of Huckleberry Finn - Mark Twain
Death of A Salesman - Arthur Miller
A Streetcar Named Desire - Tennessee Williams