Daniel Hahn in The Guardian:
It's hard not to like a book that devotes several pages to the consistency of the inner core of a walrus tusk (“a rice-pudding pattern”, resembling cucumber seeds, since you ask). The passage in question appears in a long chapter digressing on the identity of the “khutu”, which might be a fish, a bull or a giant eastern bird-god, whose horn/beak/forehead is useful in the cutlery trade, and which is not to be confused with the karkadann, which is similar, but different.
The myth of the unicorn is filled with similar-but-different and unlikely (but often true) species, with plenty of misidentifications, misleading or mendacious sources and lies that turn out to be truths. It's a testimony to Chris Lavers's skilful deployment of his arguments that his dissection of this myth is neither baffling nor stiflingly crammed with technical supporting evidence to dull the reading; on the contrary, it is lively, compelling, full of anecdote, wry scepticism and an honest humility about the things it is simply impossible for us to know for certain. (How can we be sure that a cave-painting animal has only one horn and not two, when depicted in profile?)
The book, like its subject, is not quite one thing nor another, but a fascinating hybrid. For a start, this “natural history” is just that – a study that is attentive to the natural sciences, a scientific quest into the origins of a species with real, living relatives. Our imaginary, iconic, mythological beast has a lineage linking it to the real world, many times over.