This is the prequel to "The Girl With All The Gifts" but was written second and should definitely be read second. Although it mostly deals with the events before TGWATG leading up to the abandonment of the research tank "Rosalind Franklin", the ending is set several decades in the future and ties up BOTH books with a conclusion that would be a bit spoilery, or at best somewhat meaningless, if you haven't read TGWATG first.

That said, Carey has managed to create another great book in a post-zombie-apocalyptic Britain and I liked this as much as the first, although the middle sequences of both are definitely quite similar (soldiers & scientists arguing and politicking in travelling tank). There are interesting new characters, the main ones being Stephen Greaves, a brilliant boy on the autistic spectrum who is the inventor of e-blocker, and Samrina Khan, a researcher and adoptive mother of Stephen who finds herself pregnant while on a research expedition surrounded by zombies. I'd have liked to see more of Colonel Carlysle, the military head of the expedition and the man who was in charge of the devastating and futile firebombing attempts to stop the spread of the zombie plague.

Anyway, if you enjoyed the first you'll enjoy this one as it fills in many of the missing details from the first and ties the story up in a satisfying ending.