Some of these have already been mentioned, I typed it some time ago for another discussion, some are out of print but can usually be found, but here are some of the titles on my bookshelf, (in no particular order):
Anything early (Stranger to the Ground, Biplane, Nothing by Chance, A Gift of Wings) by Richard Bach, before he got all New Agey weird and stopped writing about airplanes (though Jonathan Livingston Seagull and Illusions are fun reads if you don't take them seriously). Though I recently read Travels With Puff and enjoyed it, you just gotta ignore the parts where the airplane talks to him about the meaning of life.
Anything from Ernest K. Gann. Most of his stuff is about the years around WWII and after, but 'Gentlemen of Adventure' is about some WWI pilots and their lives in later years.
Any of Antoine de Saint-Exupéry's flying stories (some of the best, but I really have to be in the mood for his writing style).
Flight of Passage by Rinker Buck, two kids fly a Cub across the US in the early 1960s.
The Cannibal Queen , about flying a Stearman around the US, and Flight of the Intruder (a Vietnam tale) by Stephen Coonts.
The Air Devils by Don Dwiggins (the story of the early barnstormers).
Slide Rule by Neville Shute.
WWII:
Reach For the Sky by Paul Brickhill (the story of Douglas Bader, the legless Battle of Britian ace).
Fly For Your Life by Larry Forrester (the story of Bob Tuck, another Battle of Britian pilot... Tuck and Bader did not like each other).
The Look of Eagles by John Godfrey, an American fighter pilot.
Serenade to the Big Bird by Bert Stiles, a B-17 pilot.
Ultralights/microlights:
On a Wing and a Prayer by Colin MacKinnon, a Scotsman flying an ultralight across the southern US.
Global Flyer by Brian Milton, who flew a microlight around the world, more or less... he comes across as kind of a jerk, but it's an interesting read.
Propellerhead by Anthony Woodward, who decides to learn to fly to impress girls. This one alternates between "what an idiot" and "yeah, well, I did that too."
Flying With Condors by Judy Leden.
Marooned by Martin Cadin is a fictional novel about spaceflight, but has a great chapter about an 1960s USAF pilot taught to fly a Stearman by an old curmudgeon of an instructor.
Flight to Freedom by Michael Donnet. True story about a Belgian Air Force pilot stuck in occupied Belgium after Germany invaded finds a derelict Stampe biplane in a barn, fixes it up in secret, and flies to England.
Voyager by Jeanna Yeager and Dick Rutan, about the round the world flight.
Yeager, the autobiography, and Forever Flying, about Bob Hoover. Two contemporaries with very different personalities.
The Right Stuff by Tom Wolfe. Much better than the movie.
Rickenbacker, the autobiography.
The Spirit of Saint Louis by Charles Lindbergh.
Listen! The Wind by Anne Morrow Lindbergh.
A Rabbit in the Air and The Grashoppers Come by David Garnett, about flying in Britian in the 1930s.
Every pilot knows about (and should read) Stick and Rudder by Wolfgang Langeweische, but his lesser known works (A Flier's World, I'll Take the High Road, and Lightplane Flying are all worth reading.
Happy Flying, Safely by Duane Cole, about low and slow cross country VFR flying.
