In a 1995 review of the book states "In The Beak of the Finch, Jonathan Weiner vividly describes the excitement of modern evolutionary biology through the eyes and activities of two of its most important students, Peter and Rosemary Grant.

The Grants spent more than thirty years (twenty of which are covered in the book) studying the morphology (especially bill shape), reproduction, survival, and behaviour of entire populations of Galapagos finches.

[3] While the book focuses on the Grant's and Darwin's finches, it also covers work on fruit flies by Dobzhansky (Chaper 12) and Trinidadian guppies led by John Endler (Chapter 6).

The book is well received by biologists, and has been praised for its description of the ups and downs of fieldwork, the excitement of unexpected results, and the growing emphasis on critical statistical analysis to uncover patterns.

[4] It received some criticism for over-emphasizing the research by the Grants, e.g. Weiner's claim that they discovered species pairs of sticklebacks in freshwater lakes that were already well-known.