This book is exceptionally well written and paced, although descriptions sometimes become a little self-indulgent. An astounding piece of human observation, but doesn't always need to try so hard.
I like Sophie Hannah books quite a lot, mainly because they don't necessarily need to be read in sequence, I enjoy the mind games that sets them apart from the more common-or-garden police procedurals and none of the characters are ever too perfect.
However, in The Carrier, Sophie Hannah (or her editor) has completely lost her touch. Firstly, her use of letters between the characters in the narrative is pedestrian and clumsy. They all read as though Sophie Hannah has written them, not the characters themselves, there is limited difference between the voices used. This problem with indistinct voice reoccurs when she switches narrator between chapters.