If you get a copy of Sods Law Of The Sea, don't lend it out and keep it locked away. I have lost 3 copies of it so far and am looking for another.
Stan
Books by Tom Cunliffe are always worth a read. He knows his stuff inside out and his style is both easy to understand and entertaining.
Easy on the Helm is a good one, although I'm not sure it's still in print. His Complete Yachtmaster is brilliant, and despite the title deals with the topics from the ground up, including the theory of sailing.
Good luck
Martin