I ought never to have become a book reviewer. Aren’t critics supposed to resemble H.G. Wells’s Martians with their “intellects vast, cool and unsympathetic?” Instead, I’m a real softy, giving writers every possible break because I know how hard it is to produce even a so-so book. And then there’s the guilt: As 2021 ends, I can recall — to restrict myself to nonfiction — a dozen appealing biographies and works of history I meant to write about and, for one pathetic reason or another, didn’t. Let me confess some of these sins of omission.