Because the dungeons are randomly generated, every game is different. Relatively-speaking, that is. You can expect pretty much the same thing out of every game, however: a series of rooms. Some will have loot, others will have battles that yield you loot if you win. Needless to say, loot collecting is pretty central to advancement in the game.
You can only see the rooms you've been in and those adjacent to them, so exploration is the other major motivating force here. The random dungeon generation definitely helps with this, since you never know what's up ahead...except that, generally speaking, it's going to be rooms that are empty, have loot, or have monsters. A little bit more variety in the randomly generated room content would have helped make the game more compelling. (The shrines in Diablo come immediately to mind.)
Regardless, there's something to be said for simplicity, and Monsters' Den is definitely fun. If you grew up on AD&D and the games that it spawned (I'm looking at you, Eye of the Beholder), you'll probably think this game's a blast.
Biclops Games, the creators of the series, have recently released an updated version of Monsters' Den called Monsters' Den: Book of Dread. It contains the first game, plus a new campaign and a survival mode. It also contains a couple of new character classes, the ability to buy and sell items, and better in-game music.
The interface is more polished as well for the most part, though inexplicably, the character and options selection screens do not feature a "back" button. This means that once you select a campaign or a party, you'll have to either reload the game or start playing and then quit to change your selections. This isn't a huge problem, but it can be annoying. Additionally, the loading time has doubled from the first release, so those with slow connections may opt to the play the original instead.
