It seems to use billiards for inspiration. You try to aim precisely, to anticipate how the cue ball will ricochet, to hit some targets before others, and there's even a moving pocket at the bottom. In fact, it's almost like a marriage between billiards and pinball.
Unlike billiards, you get points for everything you hit. And though the formation of targets is the same every time on any particular board, the placement is different. The goal of the game is to knock out all of the red targets with ten cue balls (you can win extra balls through points or special green targets). In addition to targeting your cue ball, you also have to time your shots. If you ball is picked up by the moving pocket at the bottom, you get it back. Other times, the targets are moving.
Much of the fun is in believing you know what's going to happen when you shoot your ball, and then being
The other big factor is dynamics. As I said already, the placement of red, green, and blue targets on the board is different every time. This is huge, because it means you must use a different strategy each time you play the same board. Also, depending on the board, hitting the green targets does different things (adds pinball flippers, splits the ball into two, guides your next shot, etc), and you can eventually select which effect you want the green targets to have. There's a wide variety of boards, including ones with moving targets and obstacles.
I'm not going to review the whole thing. I haven't played the Challenges or multiplayer yet, but it's worth the price even without those modes. I've been frustrated a couple times by not being able to reach some targets (because I aimed earlier shots wrong or just bad luck), but the experience has almost always been enjoyable. So, as I said, check it out.
I've come to really respect PopCap Games. Feeding Frenzy and Zuma are also among the best arcade games on Xbox Live, and Bejeweled is a nice go-through-the-motions stress relief. I'll have to try some of their others.