Writing about science for laypersons is a tricky business, especially with regard to the scientific accuracy of the exposition and the human dimension of the characters. In the first instance, the author must choose between a superficial approach, full of analogies, fit for beginners, at the risk of boring the initiated, and a more elaborate treatment, intended for someone already familiar with the subject, that will probably scare the uninitiated. As to the characters, the author may reduce the scientists to a secondary role and concentrate on the results of research or fill the narrative with personal details about the people involved. The first choice will please the scientific-minded, while the second can make the reading more attractive to the humanists.
My main criticism of the book Einstein's Clocks, Poincaré's Maps: Empires of Time is that the author does not make up his mind about the two points mentioned above. The long expositions about relativity and chaos do not bring any new contribution to the subject; the best popular books on relativity were written by Einstein himself, while chaos theory is brilliant reviewed by James Gleick in his best-selling Chaos: Making a New Science. At the same time, the wording is sometimes confusing for beginners. As to the biographical aspect of the work, several personal anecdotes on Einstein's and Poincaré 's lives are included (some utterly irrelevant), but the book does not dwell on the rich personalities of these two giants of science.
In short: trying to please everybody, the author wrote a book that possibly will please nobody