I'll start with these ten, in no particular order. This is of course completely subjective so post yours here. The subject matter is not important. We like what we like.
Huckleberry Finn. Mark Twain.
For Whom the Bell Tolls. Ernest Hemingway.
To Kill a Mockingbird. Harper Lee.
A Tale of Two Cities. Charles Dickens.
2001: A Space Odyssey. Arthur C. Clarke.
Animal Farm. George Orwell.
War and Peace. Leo Tolstoy.
Catch-22. Joseph Heller.
The Drifters. James Michener.
The Red Badge of Courage. Stephen Crane.
Huckleberry Finn. Mark Twain.
For Whom the Bell Tolls. Ernest Hemingway.
To Kill a Mockingbird. Harper Lee.
A Tale of Two Cities. Charles Dickens.
2001: A Space Odyssey. Arthur C. Clarke.
Animal Farm. George Orwell.
War and Peace. Leo Tolstoy.
Catch-22. Joseph Heller.
The Drifters. James Michener.
The Red Badge of Courage. Stephen Crane.