A book that I got in US edition but I think also coming out in UK is titled “Marine Mammals of the World: A Comprehensive Guide to Their Identification (2nd ed).” This is by T Jefferson et alia, 2015 in this new version. I am just an English teacher with a big mammal list, not a professional ceteceanist, but to me this seems like a really good book.
As two examples, there’s a paragraph talking about how to tell apart 4 species: Fin, Sei, Bryde’s, and Omura’s Whales. It may not be as detailed as the way birding books cover vagrant buntings, but compared to most whale books, it strikes me as extremely helpful. (I missed Bryde’s whales in the Maldives and that they’re turning up on West Coast pelagics now — when I am too busy this year to go on them — frosts my pumpkin.) Another “test case” was I looked up Strap-toothed Whale. There is a very clear, seemingly (?) accurate color plate of male, female, and calf, and then in the text, 8 very good photos, including a male leaping 100% out of the water. According to the dust jacket, the authorial team has seen 117 of 129 species in the wild.
600 pages of 7.5 inches by 9 inches in US size. A brief end section does the extinct ones, eg Japanese Sea Lion and Carib Monk Seal, for those of you with a Tardis likely in your future.
Charles Hood, Palmdale California