Reference and "How To" Books
There are lots of "how to" books out there but most of them are not worth reading. The following are a few that are really worth having and reading. Keep them on board so you will have them when you need them.
Reference Books to keep on board:
Chapman Piloting: Seamanship & Small Boat Handling.
Chapman's Nautical Guides: Emergencies at Sea
Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems by Nigel Calder.
Marine Diesel Engines: Maintenance, Troubleshooting, and Repair by Nigel Calder.
Sail Power by Wallace Ross. This will help you go fast like Ol' Sailor John.
Heavy Weather Sailing. If you are venturing out into open water, you must read this. It is a collection of actual accounts of sailing vessels in storms at sea and is a study of the survival tactics that were used. It may save your life.
The Oxford Companion to Ships and the Sea (Oxford Reference) An encyclopedia of nautical history and personalities.