Reaper Man

In Reaper Man by Terry Pratchett the Death of Discworld finds himself out of a job when the powers that be fire him for developing a personality. Death is now mortal and must live out the rest of his numbered days among humans until the new Death arrives to take him away. With the Disc temporarily without a Death things can't die properly and a huge amount of excess life force accumulates causing some very strange things to happen. This is a very hilarious book. I enjoyed it immensely and highly recommend it.