I'm not much of a gamer. As a kid, I'd play a game until I felt like I knew how you'd go about writing it, and then I'd lose interest. I didn't even care to apply that knowledge, either in using it to "beat" the game (many games in those days just kept getting harder until you failed, and thus only really offered you failure), or in using it to write a clone. I knew I wouldn't play the clone, so I had no motivation to write it.
Before games even progressed to 3D, I had too much other stuff to do, so I kind of missed out on all that. I came back to gaming a couple of years ago, just after the Xbox 360 launch, when I bought an original Xbox. (That sounds perverse, but the 360 launch didn't actually mean there was anything worth playing on the 360 at that time, or that 360s were readily available, or that a handful of specific Xbox games I was interested in were on the 360's compatibility list, or that a sane human with an alternative would want to play an Xbox game on a 360.)
I'd never owned a console before. A computer that isn't end-user programmable? Not really a notion I want to support. It still bothers me, but other than "don't play games", I don't see an alternative. (Running Windows is not an alternative.)
The Xbox was ostensibly for my girlfriend, but through bad choices of games, she lost interest. I was the main user of the Xbox, and I was mainly using it to watch DVDs. Then one weekend I didn't really want to watch a DVD, or read a book, and I didn't want to write code or a blog post either. I wanted something in between, and so I bought a game.
Since then, I've played a bunch of games, found a bunch more that my girlfriend has enjoyed, bought a 360, and bought her a PSP. Gaming fits nicely into a gap on the recreation spectrum, and I've found myself thinking about games quite a lot.
What makes a game good or bad? What aspects of the implementation make/break a game? What trade-offs are visible to the user, how much do they hurt, and could they have been ameliorated? Would games be easier if there were no free amateur game guides on the net, or would they be the same and we'd still be getting "stuck" like in the bad old days? How could difficulty be managed better? Which old ideas still make sense, and which don't? How do you balance realism and fun? Why don't all games encourage playing for speed, or to kill no-one/everyone? If 360 Achievements are so fundamentally pointless and worthless and yet strangely gratifying, is there an analog for serious software ("15 G - Low Ammo: no slide in your presentation used more than 3 bullet points")? What's wrong with the Japanese and why can't they write a game I can enjoy?
Raph Koster's "A Theory of Fun" doesn't touch on the cross-over to "serious" software that interests me (the "achievements" question above), and he's not interested in implementation details either (which aren't very interesting academically, even if implementors can always learn from comparing good and bad implementations). But if you're interested in the more abstract questions, this is a great book. It might not answer many questions, but it does point out aspects and complications you might have overlooked in your own cogitations.
The style of the book is odd. Every facing page is a picture, drawn by the author. Sometimes the picture direct illustrates the accompanying text, sometimes it's more abstract. It's off-putting when you pick the book up, because it's already a small book, and it's not obvious that the pictures really add much. Half-way though, though, I was reminded of Umberto Eco's comment about the start of I promessi sposi, that sometimes text is deliberately there to slow us down. His point was that even skipping or skimming through such text helps us feel the time that's passing in the fictional world. In this book, I realized that the pictures' purpose was, as much as anything, to slow me down. The text was arranged so that no paragraph was ever split across pages, and the "blank" pages were time to think about what you'd just read. (Blank pages wouldn't have worked as well because they have no way to arrest you before you've already turned the page and started on the next.) So, ignore the style; it's a feature, not a bug.
If you're interested in games in the abstract (not even strictly just video games), I'd recommend this as an interesting read.