The USA Network advertises Monk’s new season by taunting fans with accusations of obsessive compulsion. It’s a good strategy. Obsessive compulsion is the protagonist’s affliction and the engine of his genius. The San Francisco detective and socially helpless widower Adrian Monk (Tony Shalhoub) drives his colleagues batty by needing everything just so. But his need is a potent tool for solving crimes. The show prefers a light, sometimes poignant tone but never condescends. It gets good mileage from Shalhoub’s empathic physical comedy of rare restraint. And by warmly portraying a wounded, brilliant, solipsistic shut-in who makes positive if very nitpicky contributions to society, it flatters those of us who’d like to change the world but feel strongly inclined to stay home on Friday nights watching TV.