Fasten your seat belts. Motor Mouth, second off the blocks in the Janet Evanovich series featuring Alexandra 'Barney' Barnaby, was always going to be a high-speed, high-octane ride.

This new line of comic thrillers began two years ago with Metro Girl, in which Barney, a mechanic and engineer, dumped insurance for the world of racing cars, after falling for Nascar driver Sam Hooker. Motor Mouth picks up their tale one racing season on, with Barney working in Sam's research and development team as race-day spotter - the only one on the roof in a pink lace thong. It's her dream job, but what she thinks is a serious romance crashes and burns four months in when Sam's one-night stand with a sales clerk is splashed over the tabloid front pages.

But Barney and Sam are both blond (hers, bottle; his, sun) and gorgeous and this wouldn't be Evanovich without sexual tension and raunchy one-liners. So while Sam pleads 'drunk and can't remember a thing about it, it's you I want', Barney slaps his hand away and wonders how long it will take him to wear down her defences.

Meanwhile, they join forces against big-money Mexican bad-guy hi-tech cheats on the race track. But when teammate Jefferson Warner, known as Gobbles, is locked in the opposition's car hauler and calls on Sam and Barney to get him out, things take a turn for the deadly.

What to do but hijack the hauler, stashing it temporarily in a friend's Little Havana warehouse? Enter Felicia Ibarra, a feisty Cuban granny Metro Girl readers will remember fondly, and her cigar-factory worker friend Rosa. But when they break open the hauler they find a whole lot more than they had bargained for: Gobbles, a cling-wrapped body and a billion-dollar mystery. Gobbles has overheard mention of a billion dollars worth of trouble waiting to be shipped to Mexico.

So, in just two pacey chapters Evanovich has laid the groundwork for hours of entertainment without straining a single neuron. It's all here: doggie humour, over-the-top Cuban hospitality, sexual innuendo, mystery, danger, close shaves, chase scenes and plenty of corpses.

Motor Mouth is set mostly in Florida, so there's scope for steamy weather and steamy jokes, although in the explicitness stakes this rates fairly low. Evanovich knows how to create an atmosphere without spelling out the obvious. She's less delicate about violence, and her death scenes aren't for the squeamish.

There's much about the Nascar scene, but no interest in racing is needed to appreciate the laughs. Although never a match for Evanovich's Stephanie Plum series, Motor Mouth is a clever romp of the sort that looks easier to write than it actually is.

Sadly, after a promising start it veers off course and eventually hits a wall. Evanovich's plots are wafter thin (this is no exception), but thin turns to holes - those dog jokes (Sam has a new, drooly St Bernard) and Cuban stereotypes become tiresome. And as for Sam - Barney, you can do better.