CONTEMPORARY READERS of Erving Goffman’s influential 1963 study Stigma: Notes on the Management of Spoiled Identity are often surprised at the indiscriminate way it lumps together such unlikely categories as disability, crime, pedophilia, homosexuality, mental illness, incontinence, drug addiction, prostitution, and divorce. Goffman overlooks the particularities of any one group in an effort to define a shared experience of stigma that shapes a person’s understanding of their own identity, and how they are perceived by others. Goffman’s willful disregard for difference can be explained as the product of another era, a time before identities came to be parsed along increasingly precise lines. All the more surprising, then, to find an equally audacious bundling of differences in Andrew Solomon’s sprawling new book Far From the Tree: Parents, Children, and the Search for Identity. Resisting our current tendency to divide and balkanize identity, Solomon is driven by a Goffman-like impulse to find common ground. His book is massive in every way, from its hefty 962 pages, to the weighty sadness of its stories, and, ultimately, to its ambition and generosity.

“There is no such thing as reproduction” is the arresting statement that begins Solomon’s book — one that flies in the face of any parental desire to see oneself neatly replicated in one’s own progeny. Yet with or without Solomon’s assertion, most parents come to realize that their children have personalities and motivations all their own that confound a parent’s most careful planning. “Parenthood,” Solomon writes, “abruptly catapults us into a permanent relationship with a stranger, and the more alien the stranger, the stronger the whiff of negativity.” His concern is with the outliers, those children who, by virtue of genetics, nurture, or some unpredictable combination of the two, are radically different from the parents who produced them. Who are these children? The answer to that question leads Solomon to a menu at least as eclectic as Goffman’s.

At first browse, the table of contents is off-putting: Deaf, Dwarfs, Down Syndrome, Autism, Schizophrenia, Disability, Prodigies, Rape, Crime, Transgender. Solomon’s list looks disturbingly like the kind of old-school carnival that promised bearded ladies, conjoined twins, pinheads, contortionists, and tattooed men lumped together on the same ticket. It’s worth reading past these deceptive labels, however, to get at stories of terrific suffering and resilience. Solomon is driven to understand what these seemingly disparate groups hold in common: “We are overextended in the travails of our own situation, and making common cause with other groups is an exhausting prospect.” We should resist that exhaustion, he proposes, as there is value in recognizing oneself in the experiences of others. At its best, Far From the Tree seems an urgent and necessary call for solidarity; at other moments, these identities seem connected by little more than the general assertion that we are more alike than different.

Solomon focuses on “horizontal identity,” those inherited or acquired traits that can often alienate us from our families. Where “vertical identity” consists of attributes passed from one generation to the next, horizontal identity appears suddenly and unexpectedly: an extra chromosome or a hearing impairment, a propensity toward violent crime or prodig...