Strange Bedfellows in Hot Buildings

In this dystopian, quirky tale of sex and survival, Nelson finds himself living in a 250 story building that's mostly abandoned. Along the way, he meets Guadalupe, and together they live off what's in the empty offices and apartments. Soon after their meeting, she forces him into helping her free sex slaves from a group of marauders. They fight invaders from the street and the floors above them. Eventually, they move out and have to fight to travel north. In the end, the weather begins to cool, and as it does, crops can be planted, and a kind of commune develops.
The book has a happy for now ending.