As with 1996’s Slang, Def Leppard’s eighth album marks a departure from the glossy, metallic sound that made the band famous in the '80s. On X, adult-contemporary fare like “Now,” “Unbelievable” (written by Swedish pop producer Max Martin), and “Everyday” is the order of the day, offset by the occasional heavier rocker (“Four Letter Word”), electronic-based track (“Gravity”), and lovelorn ballad (“Long Long Way to Go”). In short, this is Def Leppard all grown up.