The title is lifted from a 1963 Hank Mobley album called No Room for Squares, and the change is telling. Twenty-three-year-old John Mayer is far too unassuming to share Mobley’s ultrahip exclusiveness. Indeed, Room for Squares, Mayer’s major-label debut (he put out a solo acoustic album, Inside Wants Out, on his own in 1999), is instantly likable and accessible. But it’s no less smart and affecting for that. These thirteen songs are a travelogue of discovery — of love, identity and purpose. They may chronicle what Mayer wryly terms a “quarter-life crisis,” but they trade on energy rather than angst, wonder instead of pain. The arrangements, which are reminiscent of the deft pop of Elvis Costello and the Police, are built around Mayer’s guitar but make free use of a rhythm section and keyboards. His singing, meanwhile, recalls David Gray and Dave Matthews (with whom he shares producer John Alagia). On “Why Georgia,” which like so many songs on Room for Squares lifts into a melodic chorus you won’t soon forget, Mayer asks, “I wonder sometimes about the outcome of a still-verdictless life/Am I living it right?” He needn’t worry. On the strength of this irresistible album, the verdict on Mayer is already in.