If, like me, you have a moderate amount of knowledge of physics, you may find the brief biographical & scientific information about some famous physicists both enlightening and interesting. The book is well written with explanations of key discoveries & concepts that are necessarily brief but nonetheless do offer some feeling of clarification of what are often complex issues. And if it inspires you to read more about the scientists mentioned, then that will be a bonus.
I don't recommend digressing to read Dawidoff's 'The Catcher was a spy', mentioned because the spy in question was sent to investigate Heisenberg during WW 2, possibly with a view to assassinating him in case he was involved in developing an atomic bomb for the Germans. (This book is OK if you like baseball, & fancy a bit about the development of the atomic bomb, interspersed with a very detailed biography of a moderately interesting spy).
First of all, the subtitle of this book, "The Lives, Times, and Ideas of the Great Physicists of the 20th Century," is a bit inaccurate. Among the 8 physicists depicted in Brennan's mini-biography is Sir Isaac Newton; obviously not a denizen of the 20th century. Granted, Newton had more influence on the present epoch of physics than anyone else up until the time of Einstein, so his presence in this work is not inappropriate. It's just that he's not a 20th century physicist. On the other hand, a startling omission is Erwin Scroedinger. It is understood that one's selection of who's in & who's out can never please everyone in these types of books. However, I can't imagine someone assembling a roster of 20th century physicists without including the venerable Schroedinger. Just my opinion. The content of the personages Brennan does write about is quite remarkable. Brennan does a reputable job of describing the major motifs of different biographical epochs of each physicist, then mixing in some nice anectdotes for good measure. He also does not get carried away & deify the scientists to make them look infallible. Rather, Brennan fairly integrates their faults into his text. As a bonus, there is also a brief synopsis of the history of Pre-Newtonian physics. The most informative pages are those devoted to Heisenberg. I had always wanted to believe the stories about how he tried to sabatoge the Nazi bomb effort from the inside. Unfortunately, referencing British documents which were de-classified in 1992, Brennan nullifies those arguments as nothing but wishful thinking and ad-hoc propoganda engendered by H himself. I would highly recommend this book as a prelude for those who wish to study the lives of these great physicists more deeply. As it is a quick read, it is an equally ideal book for physicists who have only a marginal interest in the great lives of their predecessors.