Having established the meaning and referenced it against similar games I can indeed see how Isaac is, at its core, a roguelike game. It is also plainly obvious that one of the developers was also responsible for the lovely "Super Meat Boy", primarily due to the need to coat each room in splats and puddles of glorious blood.
The premise is based on the biblical story of Isaac, where Abraham is instructed by god to sacrifice his son, Isaac. The game puts its own spin on this making for a highly original concept, saturated in religious lore. Something which only an indie game would dare to do.
Gameplay is simplicity itself, trek through the dungeons, killing enemies and collecting items until you reach the final showdown with your filicidal 'Mom'. What makes the gameplay so appealing is the sheer wealth of items you can collect and the fact that each map is randomly generated. This ensures that each session is refreshing as you will never know what combination of items you will end up with or which direction you need to head in. However it can also cause one of the games few frustrations as inevitably you will get the occasional game where you can never find enough keys or bombs or decent items and you just know that you will not be suitably equipped to deal with the later levels.
Isaac rewards perseverance though and meeting various conditions will open up more items to be available in the dungeon during future play throughs. It never seems to become a chore either, this is quite a feat considering how basic the gameplay really is and is probably helped by the fact that the game itself is quite short. On a good run you could easily complete it in less than an hour.
The style of the game itself is in a league of its own, the graphics are solid, providing a range of grotesque yet cutesy characters. The fact that Isaacs appearence changes with almost every key item/power-up that you collect is a very nice touch. The environments themselves have less of an impact, just being the repeat of the same tiled walls and floors, only changing on a few occasions. This is not an issue though as too much detail here would just make the game look messy.
The sounds are suitably wet (considering that your primary 'weapon' is your tears) and the music is well suited, albeit somewhat repetitive after a while.
Technically the game seems sound though it doesn't seem to take too much before you experience some slowdown. This doesn't detract too much though, in fact it just makes the game a little easier when it is getting a bit hectic, however it seems a bit bizarre to experience such a thing on game that shouldn't be too demanding. I am assuming it is some kind of software limitation.
All in all Isaac is a highly enjoyable and easy to play game that you can easily pop on for a quick burst of gory adventuring. The amount of replay value and its inherent uniqueness makes it a bargain at its low indie price.