Photographer Paul Nicklen—who grew up in a small Inuit community in the Canadian Arctic—considers himself an "ambassador for polar life." In his Polar Obsession (National Geographic/Focal Point), the underwater-photograph specialist captures spectacular images. Accompanying Nicklen's gorgeous photos are his accounts of these creatures' habits and habitats, the ways climate change threatens them, and what it's like to move among such fierce and fragile animals. — Francine Prose