Romance writers are concerned about the love that draws two people together; crime writers, on the other hand, find far greater fascination in the things that divide us.
These take various forms, as recent thrillers illustrate.
The gender divide is what interests Lisa Gardner in The Neighbour (Orion, $37.99, pbk), although she adds an unusual twist.
The usual approach to police procedural thrillers is to start with a large cast of suspects, which the detectives gradually cut back to (they hope) the killer.
Gardner turns the whole process upside down.
In the beginning, after a young wife disappears in the middle of the night leaving her 4-year-old daughter asleep in bed, it seems a fair bet that the older husband, working nights, has murdered her.
Gardner's tough Boston female detective, D.D. Warren, who has decided problems with married men, is absolutely sure of it.
Then, it is discovered that a registered sex offender lives, unknown to neighbours, just a few doors away.
Next up is a teenager infatuated with the missing wife (a teacher), followed by a police officer who, it turns out, the wife had been having meetings with secretly.
As the pool of suspects widens, D.D. Warren becomes more frantic in her efforts to find which of the males is to blame, which Gardner brings to a crunching conclusion.
Interreligious strife and interdepartmental rivalries in Dublin are the divides in Declan Hughes' novel, All the Dead Voices (John Murray, $38.99, pbk).
Private detective Ed Loy is hired by a woman, against her sisters' wishes, to solve the mystery of their father's murder nine years earlier.
The dead man was a tax inspector who had been targeting the ill-gotten gains of three Dublin gangsters.
All three seem to have links with warring factions of the IRA and Loy discovers there are matching factions within the police and security forces, all just as much at war, as the collection of wounds Loy accumulates testify.
Most of us outside Ireland may wonder why it is so necessary to again rake over the coals of an awful civil war.
Both the fact (that Hughes has written a book which alternately glorifies the Troubles and condemns them) and the fiction (the book's plot) stir up tensions we might think best left alone.
But, of course, strife that rips a country apart rarely does go away - South Africa being another example.
Deon Meyer, in Blood Safari (Hodder & Stoughton, $38.99, pbk), explores the divide between native Africans and the Afrikaaner settlers with a story that straddles both events in apartheid South Africa and in the new, black-led republic.
Meyer's main characters are both Afrikaaners - a pretty blonde business consultant and a surly ex-convict who was, before his conviction for manslaughter, a bodyguard to a white politician.
Together, they try to trace the woman's brother, missing believed dead in the Lowveld for nine years.
An unknown group tries to stop them and after some high dramas in the bush, it turns out to have been a big-business conspiracy.
Finally, the strangest divide of all is explored in an Icelandic thriller, Yrsa Sigurdardottir's My Soul to Take (Hodder & Stoughton, $38.99, pbk).
Although the Icelandic names are something of a stumbling block to English speakers, the novel's exploration of the divide between this life and the next, complete with ghosts, a 60-year-old skeleton and some modern murders, makes compelling reading.
Lawyer Thora Gudmundsdottir's client, the owner of a spa resort which specialises in New Age treatments and is staffed by people who believe firmly in the local ghosts, is arrested by the police after the architect designing hotel extensions is found raped and murdered.
It is a grim tale in places but Thora's methodical, relentless search for the truth makes recommended reading.
- Geoffrey Vine is a Dunedin journalist and Presbyterian minister.
