The main body of the text is an interconnected set of brief biographies of six major figures in 20th century thought: Albert Einstein, a physicist; Bertrand Russell, a mathematician and philosopher; Kurt Gödel, a mathematician; Wolfgang Pauli, another physicist; and two atomic weapons physicists, Werner Heisenberg and J. Robert Oppenheimer. Readers will find solid, moderate length biographies of each of these six (about 30 pages each), with personal and professional lives intertwined. The author's background as a historian of science, rather than a practicing scientist, is clear. He emphasizes interconnections among people, their work, and the historical context. The intense discussions and disagreements of the 1920s and 1930s surrounding the switch from classical physics to a quantum mechanics viewpoint are well described. Einstein, for example, never really approved of the quantum mechanical approach, preferring a tighter connection to physical reality, stating: "He [God] does not throw dice."

A quick summary of these six lives is appropriate, since they indeed were heavyweights in a critical period. Einstein's work is well known, including the critical 1905 work on the photoelectric effect, as well as his longer study of special and general relativity and his search for a unified field theory. Russell, initially a mathematician, is perhaps best known for his later A History of Western Philosophy. Gödel worked in mathematics, proving important theorems of incompleteness. Pauli was a theoretical physicist famous for his critical probing of all new theories and theorists. His exclusion principle and prediction of the existence of the neutrino are central to modern physics. Heisenberg's uncertainty principle is another key part of quantum mechanics, and his controversial role in Nazi Germany's atomic bomb project is a good starting point for discussions of the difficult decisions that many Jewish and German scientists faced in the 1930s and 1940s. And finally, Robert Oppenheime's leadership at Los Alamos was essential to the American development of the atomic bomb, while his later political troubles exemplify the complicated relations among military, scientific, political, and personal lives in the 1940s and 1950s in America.

Unfortunately, the premise and promised focus of the book on the personal meetings of four of these individuals in Princeton is not fulfilled by the actual text. The reader quickly learns that the content of the meetings of Einstein, Russell, Gödel, and Pauli is totally unknown, and that Gödel may have been present only once. The "112 Mercer Street" context is discussed in the Introduction and Epilogue only, giving the feel that this unifying construct was added late in the writing project, perhaps after the untimely death of the primary author.

The second unifying idea, that of the loss of scientific innocence caused by the development of the atomic bomb, is also undeveloped in the book. The four main characters were not directly involved in the Manhattan project's work (although Einstein had suggested the possibility of such a weapon at the outset of the war), limiting connections to this topic. Indeed, the major professional works of these individuals had been completed well before the war, leaving them in the end stages of their careers during this period. The authors' added discussion of Heisenberg and Oppenheimer does make this connection, since both were directly involved in atomic weapons research (in Germany and the United States respectively), but neither is connected to discussions at Einstein's house in Princeton.

In summary, 112 Mercer Street is a nice collection of brief biographies of key figures in math and science in the 20th century. The overarching attempt to unify this material with very sketchy information on some informal meetings isn't successful, but the biographies provide interesting and useful information nonetheless.