At a time when hip-hop is mostly concerned with escapism, the song “That Night” is an enormous exception. The song is about Marissa Mathy-Zvaifler, a 16-year-old who was slain a few hours after a 2003 Atmosphere show in Albuquerque, New Mexico, and rapper Slug doesn’t hide behind metaphors. Sample couplet: He raped and killed her at the venue/Can’t comprehend what her friends must have went through. As these lines imply, Atmosphere’s latest disc doesn’t brim with the sort of fun alluded to in its title. Nevertheless, the recording’s bluntness (which has precious little to do with blunts) proves compelling. Slug is honest, even at the risk of embarrassing himself; after describing a booming car stereo in “Watch Out,” he admits, I must be gettin’ old, ’cause the bass sounds ridiculous. Yet he thrives amid producer Ant’s dense, old-school sonics, turning “Panic Attack” and “Bam” into aural assaults that are as aggressive as they are literate. Hip-hop fans who want only a good time won’t enjoy this Atmosphere. But for anyone interested in something deeper, it’s a breath of fresh air.