Politically it's an interesting book, in that it deals with a Northern Irish Catholic and a Southern Irish Protestant, and it takes on this issue of how a Northern Irish Catholic can be affected by Republican violence. So, ok, that's a daring move, and not an uninteresting one, but you've got to fold it into a more compelling novel, you know?
It's a sort of unlikely friendship story, two people meet randomly and end up being pals, which allows them to work through their various traumas. One problem is that while the guy's trauma is fairly intense, the woman's is a bit melodramatic and not really as compelling. I think Johnston doesn't overplay the sort of healing process for them, which is good on her part, but the story isn't really that interesting. Luckily, it's a fairly short book and you burn through it quickly.
Finally, SPOILER, the fact that the woman just had a hysterectomy because of an STD is, well, a bit over the top. I want to give her props for raising awareness about STDs and all, and I don't doubt that this could even be an entirely realistic scenario, but it comes across as completely silly.