Jack Reacher is a ex-military policeman who lives under the radar travelling around the US. He tends to run into trouble. In this case he's in New York, on the subway, and he believes he sees a suicide bomber. Reacher intervenes and the woman kills herself. The rest of the book is devoted to finding out what she was doing and why she killed herself.
The style is very much about detail. Actions are described to the level of: Reacher ordered coffee. It arrived. It was black and in a white mug. He added three sugars from rectangular white sachets with blue writing on them. This is not actual text from the novel. Short, choppy sentences tend to add urgency and increase the pace. Detail adds credibility and draws the reader into your world. With this book I realised it can go too far. There came a point when the short sentences were just grinding. The detail sometimes seemed obsessive and more about stretching the plot out to fill the word count. Although that wasn't entirely necessary as this was a big book. I did learn some interesting facts about men's tailoring though.
This was not my favourite of the Jack Reacher novels that I've read and I think that's because there was too much detail around things that weren't that relevant to the plot. The story in amongst the detail was entertaining and well-handled. I did want to know what happened and why the woman on the train had killed herself. Child does plot really well.
Character is another matter. I'm not a fan of Jack Reacher; I think he's a bit of a dick. At the end of the novel, another character accuses Reacher of letting his emotions get the better of him and it's good that we were told otherwise I wouldn't have known. The characters around him are a mixed bag. Some are drawn reasonably well, and I like that there's plenty of female characters playing non-stereotypical roles. Others are a bit cardboard cut-out. But that's ok. After all, it's all about the plot.
This is not his best, even among the few I've read, but if you're looking for something easy and light, or to examine plot, then you could do worse.