If I was forced to choose my favourite novel, this would be it.
The book is about post-nuclear America - as well as being science fiction (to a point), it also has a hint of the fantastic about it. The book follows groups of people as they struggle to survive the nuclear winter which lasts for several years, some good, some evil, who will of course ultimately clash. The fantasy part of the book is that some of the characters have "special" powers.
Critics say it is a rip off of King's The Stand, but although similar in concept, I just feel that this is written so much better. To be fair to King, it has been 15 years or more since I read The Stand, so perhaps I should give it another go.
To summarize, a brilliantly written, unputdownable classic mind-candy book. If you enjoyed The Stand, then I am almost certain that you will enjoy Swan Song, probably even more so. Give it whirl, I strongly recommend this book.