The colloquial British- and Irish-English noun bonkbuster denotes a type of popular novel characterised by frequent explicit descriptions of sexual encounters between the characters (cf. the synonymous phrase sex and shopping). In extended use, bonkbuster also denotes a film, a television programme, or even a news report, of this nature.

This noun is from bonk, referring to sexual intercourse, and -buster in blockbuster, denoting a book which achieves great commercial success.

The noun bonkbuster was apparently first used—and perhaps coined—by the British author Sue Limb (born 1946), under the pseudonym ‘Dulcie Domum’, in her humorous column Bad Housekeeping, published in The Guardian (London and Manchester, England) of Saturday 24^th December 1988:

Phone rings. It is publisher asking for photograph to put in catalogue. Also enquires about progress of blockbuster. Or as spouse now refers to it, bonkbuster. Am all too aware that wealthy heroine Charlotte Beaminster has been stuck in her jacuzzi for days because I am unable to imagine what awaits her beyond the bathroom door, but deliver glib communiqué about progress which publisher swallows.
[…]
Grab pen, and whisk Charlotte Beaminster from jacuzzi to bathroom window, from which she glimpses new gardener: stocky, balding Slav, with magnetic eyes and masterful manner with turnips. Feel at last bonkbuster is on the road.

Sue Limb explained the following in Dulcie Domum reveals herself at last, as her alter ego, Sue Limb, comes out about adultery, published in The Guardian (London and Manchester, England) of Wednesday 2^nd May 1990:

Dulcie feels she betrays her education and intellect by churning out Bonkbusters.

The second-earliest occurrences of the noun bonkbuster that I have found are from Television, by John Naughton, published in the Observer (London, England) of Sunday 14^th May 1989:

THE First Law of Newspapers says that the wages of sin are increases in publication. A glance at the paperbacks in station bookstalls suggests that it also applies these days to publishing generally. We live in the age of what is known in the trade as the ‘bonkbuster’, a paperback doorstep constructed according to a formula which requires three parts sex mixed with one part heartbreak and stirred with six parts glamour. Add a pinch of exotic settings, macho professions and unbridled wealth, steam for six months and Bingo!—you’re a celeb, hanging out your ego on the Wogan line.
In the old days, fabrication of these literary devices was a downmarket business left to siblings of Joan Collins and the like. But now simply everybody is doing one, my dear. Shirley Coran was an early runner in the bonkbuster stakes, but she has been overtaken by Judith Krantz, Jilly Cooper and—I kid you not—Susan Crosland. I wouldn’t be in the least surprised to learn that Ms Sue Lawley has one up her sleeve, or wherever it is that people conceal these things.
It was therefore only a matter of time until this malignant perversion of the publishing industry had a television programme of its very own. The Write Stuff (ITV) is just that. It goes out around lunchtime and is fronted by Anne Robinson, an exceedingly handsome lady d’un certain age who addresses the viewer in the confidential tone favoured by spivs and racecourse tipsters. The series, she whispers, head cocked coyly to one side, ‘is all about the popular books you and I like to read’. To which one whispers: speak for yourself, lady. Like all tipsters, Ms Robinson promises great things to come, notably, detailed instructions on how to construct your own bonkbuster. All you need is the ability to do joined-up writing. Or, failing that, a dictaphone.
The first programme involved sending a fresh-faced Yuppie, Richard Barber, to California where he abased himself at the feet of Jackie Collins. ‘You know,’ she breathed confidentially, ‘I do believe a lot of people in life are motivated by sex and money.’ As distinct, one supposes, from what motivates them in death. Then Ms Robinson interviewed Bob Elton about his current bestseller, before handing us back to Barber-doll to facilitate Shirley Temple Black’s puffing of her memoirs. Ms Temple Black, you will recall, is the child star who metamorphosed into a Republican politico elected on the slogan: ‘Vote For Me Or I’ll Hold My Breath’. But Barber was uninterested in politics and pressed her on literary matters, eventually eliciting the insight that ‘writing is very difficult’. Which indeed it is, especially when it concerns drivel of this order.

The noun bonkbuster then occurs in the column In The Tabloids, by Tom Widger, published in The Sunday Tribune (Dublin, County Dublin, Ireland) of Sunday 9^th July 1989:

WIMBLEDON: “The £32 million circus” screams the Daily Mirror, from a colour centrefold, and two bonkbusters filled most of the week’s tabloids. […]
[…]
A Sun News Special ‘covered’ HOW DIRTY DENTIST GOT MY KNICKERS IN A TWIST. Blonde Marie Smart went home after dentist pulled out a tooth—and found her KNICKERS were inside out, a court heard on Wednesday. Bearded dentist Stuart Allan denies indecently assaulting four women patients. The case continues.
Begin with two portions of sauce, throw in a dollop of heartbreak, stir to a frothy 84 point sans headline and you have a bonkbuster. DAME, SET AND MATCH FOR BORIS, the Sun. “Bonking Boris Becker has been spotted wining and dining beautiful brunette Claudia Blondeau while his long-time love Karen Schultz remains at home. While language student Karen has been busy with her exams, Boris has been swotting up on HIS favourite subject—WOMEN.”