If you're an ambitious reader, this book engages from cover to cover. The tone is conversational and Fearnley-Whittingstall's and Fisher's seafood knowledge is extensive. Most likely, you will use this book as a resource for thoroughly knowing fin fish and shell fish. Simon Wheeler's photography throughout the book spans from gutting fish, to cooking techniques, and to recipes with photos of the most visually beguiling seafood dishes you will ever see in print.
There are three sections: "Understanding Fish," "Fish Cookery," and "Guide to Fish and Shellfish." The book's first section discusses "Fish as Food" and offers a (very) brief human history that connects fish eating to cerebral development in humans. The chapter on "Sourcing Fish" helps readers to understand how 20th-Century fishermen acquire seafood and how some fishing practices have drastically reduced fish populations by harming eco-systems and hauling in unintended catch (i.e. seabirds and sea turtles). One of the best ways to avoid non-sustainable seafood is to be aware of harmful seafood sourcing practices.
In the second section, "Fish Cookery," every manner of preparing seafood is not only explained but shown in step-by-step photography. Preparing fish raw, salted, marinated, over an open-fire, and by cold preparation (among other methods) are explained and shown. Using seafood sustainably includes, for these authors, a discussion of "fish thrift," which means using every edible part of the fish. "Throwing away the edible parts of a carcass is quite an insult to that animal. So it's the duty of the conscientious fish cooks to use their raw materials wisely and thriftily...." This part of the book discusses repurposing fish leftovers and includes an annotated list of foods that are "friends of leftover fish," such as potatoes and eggs.
In the section "Guide to Fish and Shellfish, the authors provide detailed portraits of dozens of fin fish and shell fish along with in-season dates, spawning dates, minimum catch sizes and the Marine Conservation Society rating, which rates fish from 1 (a best rating that indicates sustainable seafood) to 5 (worst rating, indicating fish species that are burdened by overfishing or are endangered).
The River Cottage Fish Book is one of the best references for learning or broadening knowledge of seafood, and particularly sustainable seafood, in and out of the kitchen.
Fearnley-Whittingstall, Hugh, and Nick Fisher. The River Cottage Fish Book--The Definitive Guide to Sourcing and Cooking Sustainable Fish and Shellfish. Berkeley: Ten Speed Press, 2012.