Tori Amos.

A Piano: The Collection * Tori Amos * Rhino Records

"So you found a girl who thinks really deep thoughts," Tori Amos famously sang on her 1992 debut, Little Earthquakes. "What's so amazing about really deep thoughts?"

The same question could be asked of the legion of fans who've discovered Amos's compelling, probing music. For answers, look no further than A Piano: The Collection, a five-disc boxed set compiling 86 of the singer-songwriter's signature tracks, B-sides, remixes, live renditions, alternate takes, and unreleased songs. At more than six hours in length, it amply demonstrates why Amos the minister's daughter who came of age performing in the gay bars of Washington, D.C.--is one of the most enduring artists to emerge in the early '90s.

Her confessional, piano-based pop, however, is something of an acquired taste. Throughout the course of eight solo albums, Amos has intimately explored topics both tragic (rape, religious hypocrisy, miscarriages) and triumphant (survival, self-discovery, sexual empowerment), often using a cryptic lyrical code that can be frustratingly difficult to crack--"Wrap yourself around the tree of life and the dance of the infinity of the hive," anyone? What's more, her song arrangements have grown increasingly eccentric since '96's sprawling, gothic-pop opus Boys for Pele. So it's not surprising that critics tend to dismiss Amos as a Kate Bush wannabe, while radio and music channels have ignored her for the past decade, pushing her to the margins of the mainstream.

But really, that's exactly where Amos thrives. After all, the marginalized have always appreciated her most, adopting as personal anthems such emotionally charged songs as "Me and a Gun," "Pretty Good Year," and her breakthrough hit, "Silent All These Years." Unlike most of today's artists, she scores top 10 albums and sells out arenas without even trying to make her music accessible to mainstream audiences. Her subject matter and deeply empathetic lyrics are enough to inspire rabid, almost religious devotion in anyone who's willing to indulge her more ostentatious inclinations.

A far more ambitious retrospective than 2003's Tales of a Librarian--a 20-song disc that Amos dubs her "musical autobiography"--A Piano is clearly a gift to die-hard fans. It's strange, then, that it includes so many songs they already own. With a mere seven tracks unavailable elsewhere, the collection will underwhelm anyone hoping for a comprehensive collection of rare material. Stare, the live recordings, extensive B-sides, and alternate mixes are nice, but wouldn't longtime listeners prefer the elusive Michael Stipe duet "It Might Hurt a Bit" to yet another version of "The Waitress"?

Still, there's plenty to love about A Piano. Unlike much of the Lilith fare with which her work is often compared, Amos's albums have aged remarkably well--1998's haunting From the Choirgirl Hotel sounds particularly fresh--and lyrics like "So you can make me come, it doesn't make you Jesus" highlight just how daring she can be. Best of all, however, is the spectacularly revamped Little Earthquakes, now with extra tracks and resequenced as Amos originally intended--a treatment fans will likely wish she'd given each of her albums here.