When the novel she narrates begins, 15-year-old Marianne Clifford is as sweet and as innocent as they come, even if she is about to lose her virginity in the back of a Morris Minor. The sudden daring in this case, you see, is only for the noblest of causes, for she’s passionately in love with the car’s owner, a floppy-haired god called Simon Hurst who’s going to Oxford and hopes to be a writer. Arriving home after the big moment, she hardly cares if her parents, busy playing Scrabble at a baize-covered card table, notice the stains on her taffeta dress. “My days as a girl in this house are numbered,” she thinks. “Soon enough, I’m going to marry Simon and travel the world with him and eat dates in Arabia and snorkel among exotic fish along the Great Barrier Reef.”
On such dreams young lives are built or ruined – or they are at the back end of the 1950s, when Rose Tremain’s Absolutely & Forever opens. But is this a tale of true love or agonising abandonment? When Simon, having flunked his Oxford entrance exam, disappears to Paris, we begin to suspect that things may not, after all, work out between them – though Marianne lives in hope, every day at her dreary boarding school dominated now by her longing to see Simon’s “titchy” writing on a letter, his characters “like angels trying to stand on the head of a pin”. Trapped in her “love asylum”, with only her fiery friend, Pet, to talk any sense into her, she’s about to flunk a few exams of her own.
What follows is a coming-of-age story: funny, piercing and singular. For all that Marianne shares her name with the Dashwood sister who embodies the sensibility of the title of Jane Austen’s beloved novel, she’s a marvellously original creation: witty and much more clever than she thinks, but also, in a good way, quite batty. Her life now off course, she enrols at a crummy secretarial college in London, hanging out in the Kings Road as it starts to swing; gets a first job in a smart department store, and a second as an assistant to a Fleet Street agony aunt; and then, at last, marries Hugo Forster-Pellisier, family friend and trainee auctioneer. He calls her Yeti, and she calls him Anthracite, nicknames that date from a childhood holiday in Cornwall, when they played ping pong while wearing two old fur coats – and yes, there would be every possibility of happiness for them were it not for Marianne’s ongoing ache for Hurst, AKA the Paragon.
This is a slender book; some will think it slight. But each page breathes a kind of magic, a sigh of enchantment that’s hard to capture in a short review. Somehow, Tremain has imbued her 16th novel with the freshness – and the intense bitter-sweetness – of a first book of the very best kind. Its themes of adolescence and betrayal, high style and evocation of period, remind me of Françoise Sagan’s equally slim Bonjour Tristesse, though its particular Englishness also sets it apart from that book. And while the young Marianne lives in semi-rural Berkshire, and likes horses more than most human beings – the novel’s horsey sections will perhaps seem peculiar to readers who didn’t grow up on Anna Sewell or Monica Dickens – its author’s careful delineation of her parents’ brittle, golf-club ways recalls Julian Barnes’s suburban-set Metroland. The details are exquisite. Here are bath cubes, and Basildon Bond notepaper, and sauces made from marmalade to go with baked ham; whenever I see a Renault 4 in the future, I’ll always think of Pet, who tells Marianne that hers looks like “a surgical boot”.
But in the end, this gorgeous, pitch-perfect novel is a world unto itself. If it is charming and wry, it’s also eccentric (in this sense, the other book it resembles is Dodie’s Smith’s irresistible I Capture the Castle). And it’s powerful, too. Beneath its fizzy, seductive surface lies a story about big, universal things: the fog of low-grade depression; the puzzle of how one might escape the preordained circumstances of one’s life; the problem of becoming. It’s about love and hope, and the fact that wearing a skin-tight leather thong may induce multiple spontaneous orgasms – and having told you so, I can’t fathom the reason why you wouldn’t rush straight out to buy it.
• Absolutely & Forever by Rose Tremain is published by Chatto & Windus (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply