To rock critic and pop-culture journalist Rob Sheffield, any mix tape is Nirvana (sometimes literally; he’s a Kurt Cobain fan).

The mix tape, that wondrous cornucopia of sound, does not have to be a tape or even a CD; these days, it’s likely to be an iPod playlist. It can contain M’s “Pop Muzik” or Sleater-Kinney’s “One More Hour” or Pavement’s “Shoot the Singer”; Lucinda or Vanessa Williams; Roxy Music or Run-DMC or Martha & the Vandellas or, God forbid, The J. Geils Band. Some people may even own mixes on which Shaun Cassidy and/or Eric Carmen sing “Hey Deanie,” not that we would admit that in public.

To Sheffield, what’s important isn’t so much the tune as the forceful memories it evokes. “I have built my entire life around loving music, and I surround myself with it,” he writes in this funny, heartbreaking but ultimately uplifting memoir about true love, dire loss, the 1990s and why music matters. “I’m always racing to catch up on my next favorite song. But I never stop playing my mixes. ... They do a better job of storing up memories than actual brain tissue can do. Every mix tape tells a story. Put them together, and they add up to the story of a life.”

Sheffield, who writes the Pop Life column for Rolling Stone, uses his old mix tapes to build an entertaining narrative around a music-worshipping Irish-American geek grad student (himself) and a Southern Baptist girl in Charlottesville, Va., who fall in love to Big Star’s “Thirteen.”

“I realize it’s frowned on to choose a mate based on something superficial like the music they love. But superficiality has been good to me. ... For us, it was a matter of having the same favorite Meat Puppets album. ... The fact that she still owned her childhood 45 of Andy Gibb’s `I Just Want to Be Your Everything’ was tantamount to an arranged marriage.”

Sheffield and Renee married young and lived that romantic but impoverished lifestyle that always seems much more fun in retrospect. They had their own soundtracks, reproduced in this book. “Have you ever been in a car with a southern girl blasting through South Carolina with Lynyrd Skynyrd’s `Call Me the Breeze’ comes on the radio?” Sheffield asks. “Renee was driving, since she said I drove like an old Irish lady. I thought to myself, Well, I have wasted my whole life up to this moment.” They named their dog Duane Allman.

“I always pictured us growing old together, like William Holden and Ernest Borgnine in The Wild Bunch,” Sheffield writes. That didn’t happen. After five years, Renee died suddenly, and Sheffield’s world collapsed. You won’t be surprised to learn that music helped pull him back together

Told by anyone else—say, the talented but wittier-than-thou Chuck Klosterman—“Love is a Mix Tape” might quickly grow self-referential to an unbearable degree. But Sheffield deftly balances self-deprecation with heartfelt emotion, evoking horrific loss and humor with equal skill.

His observations on music and pop culture are incisive and amusing. He confesses affection for synth pop duos and ‘90s icons Clueless and My So-Called Life, and that his mix for an eighth-grade dance still makes him shiver with embarrassment.

“Why did I put Boston’s `Don’t Look Back’ on a dance tape?” He has an answer for Liz Phair’s plaintive “Whatever happened to a boyfriend?” (“I would think, Well, some of us turn into husbands, and then nobody writes songs about us except Carly Simon.”)

Love is a Mix Tape is wrenching, yes, but it’s also a glorious elegy to a pop culture-blessed decade and a tender, unforgettable tribute to the power of love.