The book switches between various protagonists who turn out to be different levels of the psyche of a man who crashed his car on a bridge and now resides in a coma.
Most (in)famous of these is 'the Barbarian' as the most primeval expression of the psyche with its close relation to violence and libido (Sigmund Freud's Id). It is also the funniest to read due to its rendition of the barbarian's prose.
The book is not typical for Iain Banks as it has a happy ending.
An amusing diversion while reading the book is working out the name of the central protagonist - it is not given, but Banks leaves enough clues to work out his forename and surname.