Here is an excellent overview of both power boating and sailing that focuses on the techniques shared by both. Solid material any boater will need to know on buying a boat and the cost of ownership, marine power and motors, technology and weather, safety, navigation, and boat handling—as well as expanded coverage on sailing and a brand new chapter on personal watercraft—this is the only boating book to own.
To be fair, if one were interested in power boating, this might be a three-star book.
For my purposes (learning to sail), better than "The Everything Sailing Book," which isn't saying much, but similar in some ways -- a fair amount of cutesy stuff, but not bad. As the title indicates, this book covers all sorts of boating -- only three or four chapters on sailing, and while there's some useful information about sailing, long lists of steps required for sailing without corresponding illustrations are fairly worthless.
Will save for possible reference -- like on knot-tying and types of line (rope to you land-lubbers) -- much of which is found in the general sections rather than the sailing section.