"Far From the Tree," by Andrew Solomon There's an old saying, one I've found largely to be true, that goes like this: You are only as happy as your least happy child. This observation isn't mentioned by Andrew Solomon in his knotty, gargantuan and lionhearted new book, "Far From the Tree: Parents, Children, and the Search for Identity." But Mr. Solomon interrogates its premise. He shakes it until your ideas about what happiness and normality are have been bent, scattered and radically realigned. Mr. Solomon's book is about diversity of a harrowing sort. He introduces us to families who are coping with deafness, dwarfism, Down syndrome, autism, schizophrenia and, in some cases, multiple extreme disabilities. He writes about rape victims who have kept their children, about the parents of criminals and about transgender children. He speaks to a luminous conundrum: how is it that many families "have ended up grateful for experiences they would have done anything to avoid"? The sprawling contents of "Far From the Tree" are difficult to summarize; indeed, Mr. Solomon has required nearly 1,000 pages, back matter included, to deliver his points. He has interviewed more than 300 families. He has shoehorned what might have been 10 or 12 books into one. His winding volume sometimes tried my patience, but my respect for it rarely wavered. Mr. Solomon is best known as the author of "The Noonday Demon: An Atlas of Depression," which won a National Book Award in 2001. He refers to his identity, in terms of that book, as "a historian of sadness." He is also a gay man, as well as a wealthy and well-connected one. His father is the chief executive of the pharmaceutical company Forest Laboratories. Uma Thurman attended his wedding. These biographical details matter for a couple of reasons. Mr. Solomon's experience as a gay child (and a dyslexic one) informs and propels "Far From the Tree." His experience in elite society has influenced the kinds of families he has chosen to profile. While some of this book's parental subjects are lower-middle-class (one family lives in a trailer park), and he traveled to Rwanda to interview rape victims, many more are successful art agents or fragrance designers or novelists or opera directors or music executives or former ballerinas or physicists at the Massachusetts Institute of Technology. His book is a Who's Who of tragedy and transformation. This can make for fascinating reading. The well born are different from you and me, at least in terms of the resources they can muster. So are the bohemian and the brilliant. I was troubled on occasion by a subtextual but darkening implication that these high-arcing lives are more worthy of parsing. Mr. Solomon's first chapter, entitled "Son," is as masterly a piece of writing as I've come across all year. It combines his own story with a taut and elegant précis of this book's arguments. It is required reading. "Our children are not us," Mr. Solomon declares on his first page. They carry throwback genes and recessive traits and are subject right from the start to environmental stimuli beyond our control. Deciding to have a baby, he says, "abruptly catapults us into a permanent relationship with a stranger."And that's the good news. Sometimes these strangers are vastly more unusual and difficult than anyone could have anticipated. Adding to the burden of caring for them is social disgust and castigation, which can be devastating and profoundly isolating. Mr. Solomon doesn't romanticize these situations, yet he argues that intense meaning can derive from them. "Life is enriched by difficulty," he says. Love is made more acute when it requires exertion. "Far From the Tree" is partly an argument for the merit to be found in extreme diversity. Discussing athletes with disabilities, for example, Mr. Solomon says, in lines that echo across this book: "Some kinds of grace would not have entered the world if everyone's hips and legs worked the same way. Deformity has been brought into beauty's fold, a catalyst for justice rather than an affront to it. Mr. Solomon fears, as do some of his subjects, that some of this wild diversity may be on the verge of vanishing from our planet. Cochlear implants are reducing the number of deaf people, a complicated issue for those among them who prize sign language as an expressive form.