This is the first time that such a comprehensive multi-authored book has been exclusively devoted to Platyhelminthes, with a strong emphasis on their phylogeny. Platyhelminthes is a fascinating group for various reasons. One is that they comprise free-living and parasitic groups but with a majority of the latter (even if free-living groups certainly play an important role in ecosystems). Another is that they offer an astonishing diversity of phenotypes, both when different groups are compared (for instance an aspidogastrean and a tapeworm) and when different developmental stages of a single species are being considered (for instance the miracidium and the cercaria of a digenean). In this sense, the cover (the ‘puzzling' Platyhelminthes …) is in itself a perfect introduction to the subject of the book. These characters make Platyhelminthes unique in the world of parasitism, and, for instance, profoundly different from Nematoda. Conversely, they are, like Nematoda, the agents of many serious (if not devastating) diseases of humans and domestic animals, which are far from being satisfactorily controlled at the start of the third millennium.

The book comprises four sections entitled ‘Early origins and basal taxa', ‘Free-living groups', ‘Symbionts and parasites', ‘Characters and techniques' and a total of 27 chapters, all written by international specialists. Sections 3 and 4 are the largest with 10 and 9 chapters respectively. One quality (among others) of the book is that even if it does not address all the topics which could fall under the title ‘Interrelationships of the Platyhelminthes', all the main advances acquired in the last twenty years in trematode evolution are summarized and/or synthesized by the authors. The origin of material, detailed literature and even matrices are often given. This gives the book a somewhat encyclopaedic character, which will be extremely useful for readers, whether they are familiar or not with the field, whether they are parasitologists, systematists or evolutionary biologists. There are approximately 110 different phylogenetic trees on a total of 420 figures. Apart from phylogeny sensu stricto, the illustrations are diverse, ranging from an impressive series of 80 scanning photographs of cestode scoleces to nicely reconstructed protonephridia and spermatozoa, and coloured schemes and photographs of nervous system organization. There is also a list of references and a detailed index (topics and taxa) for the whole book.

Although there are inevitable gaps (that the editors acknowledge in the Preface), the book is close to covering not the biology of flatworms, since this was not the aim, but the ‘great' questions, which are currently debated about the interrelationships (in a wide sense) of Platyhelminthes. Some of these debates (the basic ones ‘are they coelomates or not?', ‘are they monophyletic or not?', and many others) arose because of confrontation between the results obtained with new technologies and morpho-anatomical and/or biological traits. A very valuable aspect of the book is that, as a whole, it gives a nearly equal interest to phenotypic and molecular markers. This will prevent readers forgetting that, in Platyhelminthes as in any other living organisms, natural selection acts on phenotypes.