These charity shops are great for being a bit more random, and a bit less selective, in what you pick up!
"Game On" was, IIRC, an exhibition about computer games held around the turn of the millennium at the Barbican (although it apparently sprang originally from the National Museum of Scotland), which I rather fancied going to, but never did. I believe this to be the book of the exhibition, although it never really refers to itself as such.
It's not a literal book of the exhibition - nothing like a catalogue. Instead, it's a collection of essays on gaming, some by academics or computer journalists, and some by games players. However, the selection reveals a complete lack of curation. There are a few big names in there, from the writing-about-games side. The pieces by games players are complete duds - random, undistinguished sixth-form essays at best. There are rare interesting pieces, but I'm pretty sure you could find random better writing on the internet, even a decade ago.
The whole thing has the feeling of being edited by someone who doesn't really understand games. There's a lack of notable games designers, or artists, or programmers or whatever. There's nothing by games players who seem to comprehensively understand or be able to communicate about games. There are many academics and computer-game-book-writing theorists, but for the most part this suddenly makes me want to not read their books.
Despite being a large format arty book with tiny font, the articles are short. There are ickle screenshots largely irrelevant to the body text. The design is... medicre at best, considering it's a coffee-table book.
In short, the book is dross. I suspect it was a good thing I never saw the exhibition. The time since publication has revealed how wrong-headed it was, although it was probably pretty clear at the time. Computer games are deeply embedded in our culture now, as there are plenty of parents who have grown up with games and still play. The special handling of a nascent art form, as it seems to think it was doing, looks particularly myopic. Machinima is a non-thing. Indie games are kind of mainstream in themselves. Blah, blah, blah.
Cultural criticism of computer games is apparently difficult. Perhaps the intelligensia don't game (their loss). However, the one piece of excellent criticism I've seen is Charlie Brooker's Gameswipe, which takes pot-shots at both overly simplistic analysis of the medium, and the thoughtless games that create such stereotypical views. If you haven't seen it, watch it.