For a change, not just a miscellany of previously published pieces but essays--including two originals--with a couple of underlying themes. Generally, these pieces concern my-life-and-thoughts-about- writing, as well as insights into particular writers, editors, and scientists whom Bernstein (The Life It Brings, 1987, etc.) has known or studied extensively. This preeminent profiler of scientists for The New Yorker begins with a tribute to William Shawn, who meticulously dissected Bernstein's first 60-page piece. In other essays, Bernstein conveys what it is, in style and substance, that enables one to distinguish geniuses from cranks. There are admiring essays on Ernst (speed of sound) Mach, who could never be convinced of the reality of atoms; of Einstein, who could never accept quantum theory; and of Hawking, who sneers at ``Theories of Everything.'' Finally, Bernstein makes some startling comments on science biographies and science writing. He says that he finds confessional biographies excessive--from Watson to Luria to Turing to Feynman. At the same time, he finds Einstein's letters to his lover/first-wife absorbing and revealing, and he is quite willing to discuss Schrîdinger's well-known womanizing. Bernstein also says that he truly believes (at least in his own case) that you have to be a scientist to write about science--and that you must keep working at both vocations. Thus, he rejects the later writing of Primo Levi after Levi retired from chemistry. One wonders if Bernstein doesn't suffer the opposite of Harold Bloom's ``anxiety of influence'': Far from feeling anxiety, he wants constant dipping into the scientific waters of mentors and peers. For all one may carp with the opinions and self-righteousness, there's no denying that Bernstein writes well and sometimes even in a light vein. So readers will be rewarded to learn what happened to Tom Lehrer as well as to hear about the great and the tragic.