The novels are set in early 19th century during the Napoleonic wars. Captain Jack Aubrey and his friend and ship's surgeon Steven Maturin.
I found out about the books, when reading Donna Leon's Commisario Brunetti thrillers.
The commisario complains that he lost his daughter to a certain Captain Aubrey of the royal navy.
Who wants to join the ring:
1. Master & Commander http://www.bookcrossing.com/---/11255022/
2. Post Captain http://www.bookcrossing.com/---/11255014/
3. HMS Surprise (I am still looking for this one to register)
4. The Mauritius Command http://www.bookcrossing.com/---/11255011/
And there are another 16 parts to discover ;-)
1. Trinibell (GER)
2. Suzanne4books (GER)
3. wingpenelopewanderswing(CH) starts with part two
4. ULRK (GER)
4. Rrrcaron (USA)