'Go get lost somewhere, it always does you good.'' For Arthur Less, life is going surprisingly well: he is a moderately accomplished novelist in a steady relationship with his partner, Freddy Pelu. But nothing lasts: the death of an old lover and a sudden financial crisis has Less running away from his problems yet again as he accepts a series of literary gigs that send him on a zigzagging adventure across the US. Less roves across the ''Mild Mild West,'' through the South and to his mid-Atlantic birthplace, with an ever-changing posse of writerly characters and his trusty duo - a human-like black pug, Dolly, and a rusty camper van nicknamed Rosina. He grows a handlebar mustache, ditches his signature gray suit, and disguises himself in the bolero-and-cowboy-hat costume of a true ''Unitedstatesian'' . . . with varying levels of success, as he continues to