Somewhere around the turn of the 21st century, guys like David Gray (who'd already been labouring in obscurity for quite a while) and Five For Fighting made it hip (and profitable) to be a sensitive singer-songwriter for the first time since the '70s. Along those lines, John Mayer appeals to the kind of youngsters who are embarrassed by their parents' Dan Fogelberg collection but equally turned off by vociferous gangstas and misanthropic heavy rockers. ROOM FOR SQUARES (whose very title, not to mention Mayer's studied regular-guy cover pose, bespeaks the revenge of the nerds) accordingly trades in acoustic guitar-based folk-rock tempered with just enough 21st-century freshness to keep its practitioner in the Billboard charts (and his listeners' hearts). That's not to say Mayer's music is calculated; he's got a real feel for melody and a distinctive lyrical style. He also managed to be in the right place at the right time, and that's the key to any pop success.