Were rappers real or fake? If you claimed to be a product of the drug trade, had you actually moved weight? After Eminem’s unprecedented success for a white rapper, via “The Slim Shady LP” in 1999 and its follow-up, questions abounded. This remained a hip-hop conundrum 20 years ago - especially after the still-unsolved deaths of the Notorious B.I.G. “The Marshall Mathers LP” wasn’t a murder mystery, per se, though plenty of characters met their demise. Eminem’s second major-label album was a compelling but lurid whodunit.