This is a beautiful photo guide to the most popular anchorages of the US and British Virgin Islands. If you are planning a sail of the islands, this is a _must_ have.
I spent ten years growing up in the Virgin Islands, and went back to sail after several years away. The charter company included this book, with which I fell in love. It offers a bird's-eye view of the anchorages available throughout the VI. The clear waters and high vantage allow you to see the reefs on the page, providing the most intuitive navigation possible. It definitely makes cruising easier and more enjoyable.
Weak points are that it does not cover some major beaches (more focus on harbors) and it has little supporting text. You should also get Scott's "Cruising Guide to the Virgin Islands" or another guide book for more information about restaurants, night-life and other attractions available near the anchorages.