A truly brilliant book. With a wide ensemble cast this is a novel with a lot going on, but it's interwoven well and told at a brisk, yet not rushed, pace.

As the title suggests, this is a story about time travel. There are a ton of interesting details about how that works in this universe: for example, there are no paradoxes, you can't go back and change time, every action that future time travellers have taken in the past is already accounted for. You also can't travel to before the existence of time machines, or to after their presumed destruction in the twenty-fifth century. Time machines in this universe are all under the control of a bureaucratic organisation called the Conclave, with a callous and somewhat sick culture. As you might also expect from the title, the effect that time-travelling has on an individual's psychology is also a big focus of the book.

But it's not just a book with some fascinating premises at play – it's also a book with strongly-developed, compelling characters and an intriguing plot. The main plotline concerns a murder – a twist on the "someone is shot dead, clearly not by themselves, in a room locked from the inside" trope. The victim of the murder isn't even known until over halfway through the book. There are a number of other interesting subplots too, dealing with work, family and love (the latter particularly in regards to a lesbian main character).

The only criticism I can really make is that it wasn't exactly a page-turner; with so many bite-sized chapters I felt pretty comfortable putting this book down at any old time before diving in sometime later. As such this is perhaps more of a commuters' book than one you'd sit down to read in one sitting. In case it's not clear, this is a very weak criticism; lots of meritorious books lack that compulsive, "I must binge this whole thing now" quality and sometimes it's nice to have one you can savour (and commute with without anguish). Highly recommended!