London Rules, by Mick Herron

The fifth instalment in the Slow Horses series is another involving and fun thriller, the established characters joined by a host of new, well drawn and enjoyably fallible figures. The novel opens with a terrorist attack that is really shocking, and then a smaller-scale attack on one of the regulars. We follow our heroes' attempts to uncover what's behind these two attacks and the mounting suspicion that they might be connected.

Often the focus is on hacker Roderick Ho: his personal and home life, the thoughts bubbling away in his head, the way his perspective is completely at odds with what's really going on or what people actually think of him. This works to great effect, at once funny and suspenseful because we understand what he doesn't: that's he's in genuine danger.

Just as we think we know where we are with all this, a leading character is killed in a clumsy, accidental encounter that has major repercussions - a good example of Herron's knack for keeping things surprising and suddenly upping the stakes. As we know from previous novels in the series, no one is safe in these stories and regular characters can be killed abruptly. 

That makes the final act especially thrilling, with two regulars out on their own dealing with... well, that would be spoiling things. Herron keeps us on tenterhooks about which, if either of them, are going to survive. And then, in the closing moments of the novel, there's the tantalising suggestion that someone we thought dead in a previous book is still alive and there is more story to come...

It'll be interesting to see how this instalment is adapted for TV, not least because the last TV series ended on something of a cliffhanger about the status of Frank Harkness, the character played by Hugo Weaving. There's little mention of him here but I suspect he'll have more of a role on screen.

Again, I'm in awe of audiobook narrator Sean Barrett bringing so many characters to life. We're never in any doubt who is thinking or speaking. I made a note early on that it is sometimes confusing when we change scenes, or locations, without much pause in narration. Yet as things went on, I began to think that this was highly effective, the plot relentless and the listener required to pay attention. That and the constant guessing game of what's really going on and who is going to survive make this an immersive novel and rewarding to part of.