FORTUNE — B.B. King, Barbara Streisand, Billy Preston, Chuck Berry, Dr. John, Eric Clapton, Etta James, George Harrison, Graham Nash, Harry Nilsson, Joe Cocker, John Lennon, Keith Moon, Lynyrd Skynyrd, Martha Reeves, Carly Simon, Ringo Starr, Sheryl Crow, the Rolling Stones, Warren Zevon, and Yoko Ono.

For those of a certain age (me) that’s quite a list, and what every one of those artists has in common is this: They played with the extraordinary rock saxophone player, Bobby Keys.

The title of the book, Every Night’s a Saturday Night, pretty much reflects its feel: a little unpredictable, but spontaneous and a whole lot of fun. At 277 pages, it’s not an exhaustive autobiography like, say, Keith Richard’s recent Life. (Keith was Bobby’s good friend, benefactor, and bandmate in the Rolling Stones.) But that’s not the point. Every Night’s a great romp that is almost more of a history of modern rock than it is a look at the life of Bobby Keys. That also makes it an enjoyable and fascinating read for anyone who loves classic rock, as well as for folks who grew up on the genre.

For those of you not familiar with him, Bobby Keys is one of the great sidemen of rock ’n’ roll. He’s the unsung hero who put his stamp on some of the legendary songs of his generation. That sax solo on the Stones’ “Brown Sugar?” Bobby Keys. The sax solo on John Lennon’s “Whatever Gets You Through the Night?” Yup, Bobby Keys again. You can also hear him on legendary albums such George Harrison’s All Things Must Pass and, of course, Exile on Main Street, Sticky Fingers, and Let it Bleed by the Rolling Stones.

Now, I enjoyed reading about Bobby and his early days in Texas (lived for music; raised by his grandparents), and about debauchery on the rock ’n’ roll roller coaster (drugs, drinking, women, police, throwing a TV out of a hotel window — the usual). But I really was fascinated with the Bobby Keys-eye view of some of the recording industry’s great stars.

Ever wonder about Mick Jagger’s background vocals on Carly Simon’s “You’re So Vain?” Bobby’s the guy who made sure Jagger was in the studio on time. (He also played on that classic album.) John Lennon? You get a completely different perspective on him. If you spent any time reading the endless collection of Beatles books, you come away thinking that Lennon was just a prickly, damaged, SOB genius. To Bobby Keys, he was a warm-hearted friend. During the recording of the 1974 album Walls and Bridges, Lennon gave Bobby written charts for all the sax parts. The trouble was, Bobby didn’t know how to read music.

Lennon, with guitar in hand, took Keys into a stairwell of his apartment building and patiently (my word) taught him the parts on each song — saving Keys from “certain death by embarrassment” when he appeared in the studio with the jazz-trained session players he was supposed to supervise. “One of the million reasons to love that man,” writes Keys.

If I have any beef with the book, it’s this: There’s not nearly enough on why Keys was so in demand as a session musician, beyond the fact that he was a great guy to have in a band and that his playing style was perfect for rock ’n’ roll. In other words: What was so good about him? Keys, perhaps like his playing, just glosses over most of it. He tells us that his iconic “Brown Sugar” solo basically happened in one take. So did his solo on “Can’t You Hear Me Knocking,” also by the Stones.

There’s not much more to it in the book, but you have the sneaking feeling there was a LOT more to it in real life. Bobby’s formula in his own words: Just “blow, and whatever came out, came out.” But that’s okay. Maybe it wasn’t/isn’t all that complicated. It’s only, after all, rock ’n’ roll.