The Best of Hornblower
All of C.S. Forester's books in the Hornblower series are classics. They combine a real knowledge of the british navy under sail with great action. To me, the best of these books is Commodore Hornblower.
The action takes place in the Baltic, which alone sets it apart from the other books of the series, which usually take place in a much warmer location. The background is the invasion of Russia by Napoleon. The book touches on the diplomatic crisis that would decide the fate of nations, while serving up all the battles a lover of books on historic naval and land warfare could want.