Fever Crumb is a great book... with a rather silly name.
And I think that's probably the most disappointing part of the book. The others in the series are named Mortal Engines (taken from Othello), Predators Gold, Infernal Devices and A Darkling Plain (from a Matthew Arnold poem) which I believe are all great titles, yet Fever Crumb sounds a bit silly when compared.
However, as this is not a direct prequel and more just a book set in the same world I don't suppose it matters that much.
Fever Crumb is the main character in the book and it is her quest to find out who she really is. Along the way she will meet murderous Skinners (a group who helped over throw the previous dictatorship of the 'patchskins') insane Stalkers (cyborg soldiers) and the first of the Traction Cities.
Fast paced and full of action Fever Crumb is not a book that is easy to put down, but truth be told you probably wont need to put it down as it is sadly quite short. Fever is likeable, as are the other good characters, whilst the baddies are suitably frightening, but I cant help but feel its aimed at a slightly younger audience than the previous 4.
All in all this is a fun and exciting book which, although not as good as the other 4, is still a worthy addition to the series.