Unfortunately, Death's absence causes some anomalies. Windle Poons, the oldest wizard on the Disc, is upset to discover that, despite dying, he can't move on to the next life. As a result, he has to spend the interim as a zombie but, thankfully, he finds some help from Ankh-Morpork's resident undead rights movement. At the same time, an unusual plague of odd novelty items is afflicting the city. The wizards of Unseen University investigate and discover that something rather unusual is taking shape outside the city walls...
Reaper Man is, in the sometimes complicated hierarchy of Discworld novels, the second book to feature Death in a major role (following on from Mort and running ahead of Soul Music) and the first to feature the Unseen University wizards in a major role (although, confusingly, many of them appeared in a supporting capacity in Moving Pictures and the Librarian has been around since The Light Fantastic). Some of the City Watch (from Guards! Guards!) also crop up.
This slightly complicated arrangement probably adds to the schizophrenia of the novel. In all of the Discworld books prior to this, the storylines usually converge at the end and the story is usually quite focused. Reaper Man instead sprawls, with Death/Bill Door's adventures and the subplot of the wizards/Windle Poons not really gelling together. There is a vague link between them, but otherwise the two stories don't really intertwine, resulting in a rather disconnected feeling to the book. This is added to by the wizards stuff being quite funny and the Death stuff being quite serious (the advent of the Death of Rats aside).
"You can't trust those voodoo gods. Never trust a god who grins all the time and wears a top hat, that's my motto."
"Is it? That's a funny motto."
- two of the wizards
Pratchett is also pursuing another satirical target here, following on from films in Moving Pictures and police procedurals in Guards! Guards! Unfortunately, the target is rather weak - Pratchett apparently doesn't like shopping malls, hates muzak and isn't keen on combine harvesters - and there's a distinctly half-hearted feeling to proceedings here. The book never really seems to come together and fire up like the best books in the series, despite many individually good moments and some funny lines. Ultimately this appears to be a case of Pratchett trying to be serious and even moving but also trying to throw some chaotic comedy into the mix as well, and it doesn't work. It's notable that when Pratchett separates the two out - as he does in the double-whammy of the more serious Small Gods and the funny Lords and Ladies - he does very well, but the mix here does not work as effectively.
Reaper Man (***) is readable and interesting, but definitely one of the less successful books in the series. It is available now in the UK and USA.