This combination book/e-book covers every shallow-water species of crab and shrimp found from the Aleutian Islands to the Mexican border: nearly 300 in all, in full color. This is the ideal guide for the beginner and the professional alike, offering a user-friendly introduction to these fascinating animals while also providing the detailed references and other resources needed by those specializing in the field. The unique print/e-book format allows readers to choose their own level, whether browsing the hundreds of photos that show the beautiful colors and interesting shapes of the varied species, or trying to identify the most challenging specimens under a laboratory microscope. The print book includes numerous (and often humorous) sidebars covering all sorts of topics, from interesting tidbits on the behavior or biology of the animals to historical vignettes. The accompanying cd contains all of the species profiles in a convenient pdf, so it can be put on a phone or tablet to take anywhere. Every piece of information in the pdf is hyperlinked to the full reference (2,600 links), while hundreds of other links connect to additional photos that show particular features, comparisons to similar species, and even short video clips showing various behaviors. Interactive keys to many of the groups are also provided, including both a color key for identifying live hermit crabs and a separate one for preserved specimens that have lost their color.