In her 12th novel, the Booker shortlisted Roberts (The Looking Glass) presents two London writer-sisters in their early 50s locked in a slow-motion love triangle. The more practical Catherine, whom Roberts makes pointedly slim, teaches part time at a local college, writes pornographic novels using an alias to supplement her income and is married to Adam, a critically well-regarded though not commercially successful novelist. Vinny, a poet, has a spotty employment record and a thicker waist, but takes literature much more seriously, and had known and loved Adam first. In a series of flashbacks, Vinny loses him to Catherine on a vacation the three take to France to visit Adam's father, Robert, a painter who has a house there. The novel progresses in an undemanding and not unpleasant free, indirect style, and readers may find themselves rooting for warmer, more tolerant and honest Vinny to become reinvolved with Adam, who has grown weary of Catherine's adept negotiations with the world. That story is intercut with a subplot that turns on Vinny's love for Charlotte and Emily Brontë and includes the by now somewhat tired gambit of fictionalized letters that invert the main story; Charlotte writes to her former teacher at a Brussels boarding school, Monsieur Heger, whom she loves with a searing passion despite her marriage to a clergyman. Roberts delivers familiar midlife pathos, longing and literary frisson unpretentiously and with enough flourish to hold interest throughout. Agent, Gillon Aitken. (Sept. 10)