Annapolis Book of Seamanship
Chapmans Guide to Piloting
Are two heavy weight (as in big and thick) books you can keep through a lifetime of sailing or power boating. They cover most elementary and advanced topics as far as a one book does all type of thing. The details and references in them are thing I still go over.
The American Practical Navigator was originally by Nathaniel Bowditch is a available free as a PDF file from the NOAA web site
Maritime Safety Information . It originates back to the early 1800's but has been updated over the years and includes a great discussion on Navigation. This PDF version is from 2002. it's a 40MB download and includes 882 pages. It has a full set of sight reduction tables and other references for navigation. You can also buy the printed version too.