William Nicholson is one of our most underrated novelists, a subtle and addictive writer who deserves to be a household name. As prolific as he is multitalented, he's the screenwriter behind Gladiator and Shadowlands, as well as writing fantasy and teen novels. His fans  and I am one  sometimes wish he would concentrate more on his adult books.

Here Nicholson transports the flavour of The Unbearable Lightness of Being to Joanna Trollope's landscape as he follows, over six days, the lives of a group of middle-class bumblers living in a Sussex village.

Ostensibly the story centres around the seemingly idyllic marriage of Laura and Henry, as Laura receives a letter from Nick, a man with whom she had a passionate affair 20 years ago. Her self-obsessed, frustrated husband has never been any match for Nick's dynamism and she knows it. The reader knows she has  at most  a week to make up her mind whether she is in or out of her marriage.

Henry is a brilliant, tortured character, hating himself for his success as a documentary director, always upstaged by the idiotic posers who front his programmes. His disillusion is shared by the other characters whose lives are discreetly doomed by the failure to act with any honesty or daring: Alan, the teacher still kidding himself that really he's a playwright; Liz, the single mother who can't stay away from her manipulative ex; Marion, the disturbed woman with designs on Alan; the vicar who is questioning his faith.

Somehow Nicholson avoids any of this becoming twee, with his remarkable eye for detail and for the weaknesses of human nature. There is an undercurrent of lust throughout the novel, somehow poignant, sometimes comical. He moves slickly between his characters, pulling away unpredictably just as we think we've got to know them. You can almost feel him panning cinematically across their lives.

More commercial than his previous adult novels, The Trial of True Love and The Society of Others, this is an interesting departure for a writer who knows his way around the human psyche. In Nicholson's capable hands, the cosy setting becomes uneasy and the familiar takes on new meaning: think Midsomer Murders but with existentialism instead of murder. The sequel  All the Hopeful Lovers  is out in September. Can't wait.