It seems your Go teacher has mysteriously disappeared, but she's left behind some clues. The clues lead to a sort of larger-than-life Go board, which you have to navigate, by turns using your Go knowledge and your common sense. The puzzles you encounter along the way are mostly logical, with a few exceptions, and their structure blends symmetry and asymmetry in a way appropriate for the underlying game of Go. If there are problems, they're largely motivational: most of the puzzles are premised on something akin to "here's some stuff to fiddle with, and if you fiddle with it properly, you'll have something that will eventually prove to be useful," rather than actual goal-driven reasoning. Still, Not Just a Game has a lot of company in that respect, and it's hardly a fatal flaw. There's also an interesting blend between chinoiserie/Orientalism and Western culture, in that the bulk of the puzzles that aren't directly related to Go could fit into your average house-setting or fantasy game, and there are certain objects (e.g., chewing gum) that would seem a bit out of place if the game were really striving to be culturally correct. In fact, the game itself calls attention to this contrast--the initial room description puts a Go board "between the sofa and the TV," and the description of a computer mentions that your teacher "doesn't feel comfortable around technological equipment." (Quick disclaimer: I'm not saying technology is Western. Merely that late-twentieth-century stuff like computers don't fit all that well into the chinoiserie setting, as exemplified by Sound of One Hand Clapping, or, for that matter, the endgame of Not Just a Game.)
The aspect of the game that requires that you actually apply Go knowledge in more than a superficial way isn't quite as successful, unfortunately. It may be that Go just isn't easy to learn from a few entries in a booklet, but the Go problems that appear at the end of the game were difficult enough that I often didn't understand why the correct solution was correct, even after I'd found it by trial and error. This might be my mental block, but I'm not sure that applied reasoning on this level, even if it's only to learn Go, is well suited for IF--at least, barring a more thorough tutorial process than Not Just a Game provides. The final puzzle, which essentially involves scoring a completed Go game, is tedious in the extreme, moreover--once you figure out the premise of Go scoring, which isn't all that complicated, it's a matter of counting dots on a large grid. Whereas the other puzzles felt obscure, this one just feels mindless--and the game would benefit considerably, I think, if it were removed.
The writing is quite good--it's rarely especially evocative (the setting is largely pretty unremarkable, after all), but it also rarely gets in the way of the game, which takes some skill in itself. There's also some humor scattered here and there, documented in an 'amusing' section. There are likewise few technical flaws or game design problems: one section involves a lot of traipsing around, which does get tiresome after a while, but at least it's straightforward traipsing. The story itself requires some disbelief-suspending, but no more than your average fantasy game, to be fair--and the only reason that the suspensions of disbelief here require a conscious effort is that the initial genre of the game isn't clear from the outset, and the setting wanders back and forth a bit between Western suburbs and, um, a vaguely Oriental setting. That may be jarring initially, but it's also rather creative, and it allows for some interesting juxtapositions. For instance, the "Five Elements of Chinese Philosophy" can be found in a poster on a refrigerator, and a baseball bat figures prominently in putting together the Go-related materials. The picture that emerges is one of cultural synthesis, in some respects: your teacher clearly is struggling to retain her own values in an unfamiliar culture, and yet you--and she, implicitly--are surrounded by the trappings of that culture, and draw on them to achieve your ends. The cultures are more complementary than conflicting, then--it's not a question of rejecting one in favor of the other. (I must say, though, that the computer with Z-abuses on it was an odd touch, even under a cultural-synthesis analysis.) In that light, then, it's not necessary to believe uncritically that, as your teacher says, Go is "a reflection of your inner self"--merely that there are many for whom the game of Go really is that important, and that it's worth examining the implications of those values.
As a game, then, Not Just a Game is quite solid, if hardly extraordinary. The puzzles are good, and reasonably creative, but nothing particularly remarkable, and the Go puzzles themselves don't work particularly well. But among the subtexts are some rather unusual IF themes, unusual enough to make this one of the more interesting recent works of IF.