Bill Walton arrived at the San Diego Natural History Museum carrying a large black chair. I watched him walk with it, a little stiffly, past the Moreton Bay fig tree outside. The tree is one of the city’s grand natural treasures: more than 100 years old, nearly 100 feet tall, hugely spread, still standing despite a century of weather and air pollution and climbing children. It’s so large that it made even Walton, one of basketball’s dominating giants, look small.

“Why is he carrying a chair?” the woman working the museum’s front door asked me.

I had no idea. We were standing inside the building, near the skeleton of a dinosaur (Allosaurus fragilis, the sign said), watching him approach. Walton wore jeans and a Grateful Dead T-shirt. He chewed gum. His hair, formerly long, red and curly, was now a sparse white wisp. His stride was deliberate, determined; each step seemed to cost him something.

Walton is another of San Diego’s grand natural treasures: a 1970s basketball superstar, celebrated sports broadcaster, proud public hippie and — to quote the man himself — “the most-injured athlete in the history of sports.” He is now 63, at least in regular human years, but his body has always operated on some other, more severe time scale. His injuries have been relentless; his life story reads like a jock Book of Job. Walton has had 37 orthopedic operations, many of which came at the worst possible moment. The biggest difference between him and any of the other greats you’d care to name — Michael Jordan, Bill Russell, Kareem Abdul-Jabbar, Wilt Chamberlain, Shaquille O’Neal, Larry Bird — is that Walton’s brilliant career barely ever happened. Instead of winning the three or four or five or six championships he seemed destined for, Walton became a legendary failure. (He did manage to win two.) His injuries caused him to miss nine and a half of his 14 N.B.A. seasons.

I had come to San Diego to speak with Walton about his life: the magic rainbows interweaving over the bottomless, flaming abyss. He tells that story in his new book, the amazingly subtitled “Back From the Dead: Searching for the Sound, Shining the Light and Throwing It Down.” For an athlete’s biography, the book is surprisingly fatalistic: It begins with Walton on the brink of suicide and ends with many of his friends dying. It suggests an existence largely shaped by dark matter — all the things that didn’t happen, that never coalesced, that went missing.

And now here he came, walking on his ruined feet. The chair Walton carried did not look, in any normal sense, portable. It was tall, unwieldy, rigid, nonfolding. It looked like a piece of lawn furniture. But no: This turned out to be Bill Walton’s personal chair. He carried it with him everywhere, as a snail carries its shell.

In fact, these were the first words he said to me: “I love my chair.” And then he said it again: “I love my chair.” He said this with the kind of affection that most people reserve for children or pets. This is because Walton’s chair and its unusual qualities — its sturdiness, its high elevation — are the keys to the health of Walton’s spine, and the failure of Walton’s spine, not so many years ago, nearly made him kill himself.