DETROIT – Guess who’s back?

Shady’s back.

So is Eminem, and Marshall Mathers, too.

Whatever you might call him, the man recently named the “best rapper alive” by a poll of Vibe magazine readers has returned in a major way. The 36-year-old superstar’s re-emergence comes four years after his last studio album, three years after he was treated for a sleep medication dependency and two years since the violent death of his best friend and the collapse of a second marriage to his childhood sweetheart.

His new track, “I’m Having a Relapse,” has caused a stir on the Web and is fueling talk of a new record and maybe even a tour.

But before Eminem moves forward musically, he first is taking a step back with a memoir out Tuesday that shares quite a few revelations about a man whose autobiographical lyrics have tantalized fans for years.

In “The Way I Am,” the man born Marshall Bruce Mathers III takes readers into his painful childhood and adolescence and inside the studio and beyond as the former Detroit factory floor sweeper and short-order cook enters the rap game and becomes a worldwide hip-hop sensation.

The book is 200-plus pages worth of text, behind-the-scenes photographs and reproductions of Eminem’s original lyric sheets – hotel stationery and other scraps of paper he used to scratch out partial verses of the songs that would make him famous: From “My Name Is” and “Stan” to “Lose Yourself” and “Without Me.”

Eminem may not love being in the public eye, but he loves music, and that’s drawn him out, said publisher Brian Tart, president of Dutton Books, an imprint of the Penguin Group (USA) Inc.

“I think he doesn’t like being famous, but he sure likes being an artist,” Tart said. “Getting away from the trappings of fame was something he needed to do. But in his bones and his blood, he’s an artist.”

The book kicks off with a prologue that provides one of the reasons Eminem has shunned the spotlight for the past few years. He describes in-depth just how difficult it has been for him to come to grips with the loss of his longtime best friend and fellow rapper Proof (Deshaun Holton), who was gunned down at a Detroit after-hours club in April 2006.

“After he passed, it was a year before I could really do anything normally again,” Eminem writes. “It was tough for me to even get out of bed, and I had days when I couldn’t walk, let alone write a rhyme.”

“I have never felt so much pain in my life. It’s a pain that is with me to this day. A pain that has become a part of who I am.”

It was Proof, he says, who not only urged him to become an emcee, but also served as a “ghetto pass” – allowing the white Eminem the street cred he needed to enter Detroit’s black-dominated hip-hop scene.

“If Proof hadn’t gotten me … into the rap game, I don’t know where I’d be,” he writes. “I certainly wouldn’t be someone you’ve heard of.”

But millions of people have heard of him, and what they know of Eminem largely is based on his lyrics, his outsized public persona and the 2002 semi-autobiographical film, “8 Mile.”

“The Way I Am” answers a few lingering controversies and questions, including his 2000 arrest for pistol-whipping a man who kissed his wife (“Guns are bad, I tell you”); his substance-abuse problem (“I’m glad that I realized it and set myself in the right direction”); the flap over his perceived homophobia (“Ultimately, who you choose to be in a relationship with and what you do in your bedroom is your business”); and ethnicity (“Honestly, I’d love to be remembered as one of the best to ever pick up a mic, but if I’m doing my part to lessen some racial tension I feel good about what I’m doing.”)

Eminem also recounts his early years, living in public housing in Savannah, Mo., before moving to Detroit. He discusses the hurt he felt at never having known his father, the complicated relationship with his litigious mother and the suicides that ended the lives of his two uncles.

After he made the move to the Motor City, Eminem describes being a quiet outsider at school, having his home repeatedly robbed, getting pummeled by the police and later bouncing between dead-end jobs trying to make ends meet to provide for his then-wife, Kim, and daughter, Hailie.

But things turned in his favor when Proof urged him to start rap-battling at Detroit’s Hip Hop Shop. He made a name for himself in his home city by trading insult rhymes with fellow battlers and eventually branched out, competing in rap battles in Ohio and California. It was in Los Angeles that Eminem was spotted by an assistant in the office of Interscope Records executive Jimmy Iovine.

Before long, rap icon Dr. Dre came in to help produce what would become Eminem’s ticket to stardom, 1999’s “The Slim Shady LP.”

While the pair had worked out the songs, Dre said the album lacked the image of what the Slim Shady character should look like.

A drug-fueled impulse buy took care of that problem.

After two hits of Ecstasy, Eminem popped into a drugstore and on a whim purchased a bottle of peroxide. He threw some on his head and the platinum blonde hair and white T-shirt Slim Shady look was born.

“I wasn’t thinking that the peroxide thing was going to be my look,” he writes. “I was just being stupid on drugs.”

(It should be noted the book features a humorous passage in which Eminem describes having invented the Slim Shady persona during a moment of clarity … on the toilet.)

The record ended up being a smash hit, as did two that came later, “The Marshall Mathers LP” and “The Eminem Show.”

In all, he has won nine Grammys and an Oscar.

And along the way, he’s had more than a few quirky high-profile run-ins, many of which he touches upon in the book: a fling with Mariah Carey, a performance with Elton John at the Grammys and the televised tiff with hand-puppet Triumph the Insult Comic Dog.

Still, as he prepares to again enter the public eye, a more grounded, mature Eminem says he’s trying to keep everything in perspective.

Music is important, but being a father to three girls – Hailie, niece Alaina and another girl, Whitney, who isn’t biologically his – is where it’s at.

“All three of my girls call me Daddy,” he writes. “They’re all loved the same and they all get the same treatment.

“Because of my success, I’ve been able to provide for them in ways my family never could for me. That’s what it’s all about.”