Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the 30,000-plus fish species known to science.

After a short section on Chordata and non-fish taxa, the work lists all known fish families in a systematic fashion.

Notable genera and species are mentioned, though the book does generally not deal with the species-level diversity.

The complexities of the higher taxa are described succinctly, with many references for difficult points.

The fourth edition was the first to incorporate the wide use of DNA analysis, revising many earlier classifications.