Best comprehensive study of World War I?

Answer 1

There are 4:

1) The First World War, by A.J.P. Taylor
2) The First World War, by John Keegan
3) The First World War, by Martin Gilbert
4) The Pity of War, by Nial Ferguson

The Guns of August, by Barbara Tuchman, is a GREAT book about the first month of the war.

The best Novels are:
A Farewell to Arms, by Ernest Hemingway
All Quiet on the Western Front, by Erich Maria Remarque