The book starts with a look at other claims of the death of postmodernism, which it seems often come from small groups insisting that their idea is going to be the next big thing. Kirby's claim is not like this, the ubiquity of digital technology is fairly indisputable. He compares the user generated content of Web 2.0 with earlier ideas of the reader's role in accessing literary works, but is keen to point out that Web 2.0 is far from delivering the collaborative works which some might have hoped for. The book also looks at changes in popular entertainment, showing how children's films, for example, depend more and more on references to earlier works.
Kirby comes from a postmodernist background, so his style of writing might not suit all readers, but I felt that in predicting the end of postmodernism he distanced himself somewhat from its worst excesses. If you would like to see a different take on the digital revolution then you may well find it of interest.