A soggy sandwich with a great filling...

Twenty years ago, Róisín Burns had to flee her home in Northern Ireland after getting caught up in the Troubles. Now the IRA man she fled from, Lonergan, has reinvented himself as a politician, and Róisín has returned to take revenge, sort of. Or something.

This is another of the ubiquitous trend for books set part in the past and part in the present and, like so many of them, one part is much stronger than the other. The past section is set at the height of the Troubles, and Neary gives a convincing picture of a young girl trapped into doing the IRA's bidding in a city where fear is a constant presence. The present is a silly thriller with absolutely no credibility whatsoever and drags interminably. In fact, I came close to abandoning it before I even got to the past, since it takes almost a third of the book to get there, apart from the brief prologue.

Róisín, now known as Sheen, has turned up on Lamb Island off the coast of Northern Ireland, where Lonergan now has a cottage. Sheen rents a little cottage too, isolated of course, just up the road from the resident nutter whom everyone assumes murdered the previous woman tenant. They don't bother to tell Sheen this though, contenting themselves with warning the nutter, Boyle, to behave himself. He doesn't. But he's not the only bad man on the island – for such a small population it seems to attract more than its fair share of men willing to bump off lone women, for personal as well as political reasons. We spend an inordinate amount of time inside Boyle's foul-mouthed and lustful head – ugh! Tedious in the extreme.

Then we go back to Belfast to what seems like the mid-'70s, though we're not told exactly. The Troubles are at their height, with frequent beatings and bombings directed at both British soldiers and civilians fairly indiscriminately. This section feels almost as if it's written by a different author. The city and its people are recreated with a real feeling of authenticity, and Neary raises a lot of intriguing questions about where moral responsibility begins and ends in a situation where the norms have disappeared and law and order have almost completely broken down. At first Róisín is tricked into helping the IRA, but after that she has to make choices – pay the consequences or continue down the path of terrorism, this time knowingly. Neary shows how grey that question becomes in a sharply divided society, where informers on either side are at extreme risk. She also touches on the question of how far the crimes of the past must be forgotten or forgiven in the pursuit of peace.

And then sadly back to Lamb Island for a ridiculous thriller ending. The idea is ludicrous that a middle-aged woman with no combat experience or training would decide to take on members of the IRA whom she knows have no compunction about killing. And so unnecessary, since if Róisín simply wanted to destroy Lonergan, she could have sent an email to the police or the newspapers from the safety of her American home. But instead she comes back to Ireland to face Lonergan herself, to... I'm not really sure what... threaten him? Shame him? Neither tactic likely to work on an IRA terrorist, I'd have thought. And then it gets even sillier...

So a mixed bag. If Neary had stuck to telling the real story – the one in the past – this could have been an excellent book. Instead it's like a sandwich with a great filling, but slapped between two thick pieces of soggy and underbaked bread. Maybe it's time for authors to start telling one story again, instead of feeling obliged to stick in an extra timeline and a thriller ending – as all trends do, this one has seriously lost its novelty value. 2½ stars for me, so rounded up.

NB This book was provided for review by the publisher, Random House Cornerstone.