Inferno is based upon the hell described in Dante's Inferno, however it adds a modern twist to the story. The story is told in the first person by Allen Carpentier, a science fiction writer who died in a failed attempt to entertain his fans at a party. He is released from a bottle in the First Circle of Hell by a man named Benito, who offers to take him out of Hell by bringing him to the center.
At first, as Allen and Benito travel through Hell, Allen tries to scientifically rationalize everything he sees, renaming his surroundings as 'Infernoland', a high-tech amusement park some thousand years in the future. It isn't until he sees a man recover from incineration and his own leg heal from a compound fracture that he actually believes he is in Hell. From this point on, as he travels through the inner circles of Hell, he sees how he is guilty of each of the sins in some fashion. Allen views the punishments for these sins as far surpassing the crime, repeatedly thinking, "We're in the hands of infinite power and infinite sadism."
Niven has stated that he is working on Purgatorio, a sequel.