The reader has very definite expectations of Joanna Trollope. She has, after all, had the commendable wit and excellent good fortune to create a genre. She always deals with the reality of English provincial lives. She always builds her novels around the flash point of a personal drama (love and death, divorce and bankruptcy). She takes care to pepper them with consumerist details (tins of butter beans, five-stone engagement rings and, of course, those cast-iron things country folk like to cook on). She’s a sort of slightly soiled realist (she could never be dirty) for the middle classes.

The Best of Friends is firmly set in middle England, in ‘Whittingbourne’, and it centres on two couples. Fergus is married to Gina, and they live in a gracious historic building with their only daughter, Sophy; Laurence and Hilary live with their three teenage sons in a happy, messy flat above the very nice hotel which they jointly run. They are the title’s Best of Friends. Then Fergus drops a bombshell: he is leaving his wife (fleeing, as they always do, to London), and the fallout reverberates violently around the two families. A battle breaks out between Gina (small, shiny, self-obsessed and citrus-smelling) and Hilary (larger, capable, bespectacled and more cinnamon in flavour) for the love of Laurence, and poor, wan Sophy is caught in between.

Marital breakdowns are Trollope’s forte. She shows here – as she showed in A Village Affair and A Passionate Man – an acute understanding of how they can suddenly, arbitrarily erupt, and how far-reaching can be their consequences. As usual, she works hard to give everybody’s point of view, but, as usual, the women get the best tunes (and Gina, here, is the devil). In comparison to their wives, Fergus and Laurence are of cardboard depth, and compared to Sophy, the teenage boys are just smoky, smelly, scruffy clichés. But that’s because Joanna Trollope knows only too keenly what it is that her public wants.

Every few pages, things are planted by an expert – some might say cynical – hand to provoke a chuckle or a sigh of recognition from her readers: little examples of male ingratitude, teenager’s bedrooms like ‘bear pits’, middle-aged exhaustion, UCCA forms, piles of laundry, middle-aged love, financial worries…It is the conscientious accumulation of domestic detail familiar to so many family lives which explains her enormous success. And The Best of Friends will be an enormous success. It is as highly readable as all her other sagas … In fact, it’s pretty indistinguishable from all her other sagas. It is the most common criticism thrown at Trollope, that all her books are just the same. But who can blame her? If you’re winning the jackpot, why walk away from the fruit machine?

It must be said that lately, instead of cherishing the genre to which she gave birth, she has begun to toy with it. In A Spanish Lover, her last, sixth, novel, she went a bit far – to Spain, in fact, which isn’t actually very far, but the fans thought it so. A good half of the story was about villages in Andalucia (instead of sensible Gloucestercia) and Catholic cathedrals (instead of sensible Anglican ones). That is not what is expected from the works of Trollope minor and although it sold as well as ever, it is not one that true aficionados recall with a tear in the lightly mascaraed eye.

The Best of Friends is not one of her Oh-the-pleasures-and-pitfalls-of-village-life numbers. Whittingbourne is no mellow Cotswold stone village, but a market town threatened with a bypass and a DIY megastore. The Woods and the Bedfords are striving rather than affluent middle-class, and both families have to work hard for a living. No one goes to church. There is no hint of any private income, for a change – indeed, Gina’s mum, Vi, lives in sheltered accommodation, swears rather a lot and deals in double negatives (as in ‘you can’t do nothing for yourself).

There are no toffs to speak of, no horses, no mandatory large dogs; the only pet is a budgie in a cage. And what’s more, there isn’t even an Aga. Well, there is, but neither the Woods nor the Bedfords own one. It isn’t a main, lead-role, always-there-in-times-of-stress, curl-up-beside-it-and-have-a-good-cry Aga. This one just has a walk-on, comedy part. It belongs, you see, in a London kitchen! ‘It’s my dearest friend,’ says … a Londoner. The first recorded use of the Ironic Aga … Joanna Trollope may be back on her home turf, but beware, she’s beginning to fidget rather.