Excellent, comprehensive guide devoted entirely to PEI.
This was the most comprehensive and up-to-date guide to Prince Edward Island. While other major travel guide's treatment of PEI was limited to a small section in the back of a Nova Scotia guide, the aptly-named Colourguide provides a colorful, comprehensive guide to the island.
Great balance of history, practical information, and gorgeous photography. (I purchased a second copy for my mother, who especially enjoyed the section on the birds of the island.) I was especially excited to see equal and extensive treatment for the attractions outside of "Anne's Land."