I bought this trying to ease my kids (ages 6 and 8) into the wondrous world of Ye Auld Game. It has been a big hit and would be worth at 5x the asking price.
Unbeknownst to my kids, but obvious to their old man, Megadungeon (hereafter "MD") is clearly inspired by that grand old TSR game, Dungeon. Like that pioneering effort, you select a type of adventurer and then enter the dungeon, which consists of corridors and rooms. Each room holds a Monster and a Treasure. You kill the former and take the latter, trying to amass enough gold to win the game.
But MD takes that idea and puts a lot of new spins on it. Principally, unlike the preset underworld of Dungeon, that of MD is randomly determined as you play. Thus, not only is it different every time, but the players have only a limited idea of the layout, giving MD a (slight) exploration aspect that its predecessor entirely lacked and which is an essential part of old-school D&D. One major effect that this has on play is that you cannot easily choose in which level of the dungeon you wish to adventure; you start on Level 1 and cannot proceed until you find some stairs.
Another significant difference is that the various classes all need the same amount of wealth to win. Thus, unlike in Dungeon, where the Elf was significantly weaker than everyone else but also need less treasure, it is important that all the classes in MD be balanced in effectiveness. That leads to one of the few problems I had with the game.
I have now playtested the Sorcerer class about a dozen time and can confirm that it is remarkably less effective than the Warrior or Rogue. In theory, his spells should give him more power than the others, with the trade-off that he has to rest frequently an replenish his power. In practice, however, the two spells he gets at the beginning of the game are fairly useless (Dazzle gives him a +1 bonus to attack, but his attack strength is so weak that it doesn't amount to much). Higher levels spells are a bit better, but the Sorcerer will have fallen so far behind the others by the time he gets access to them, that it is a moot point.
That said, MD is simple enough that it is easy to add rules and tweak things. I have come up with a house-rule that seems to work pretty well for the Sorcerer, for instance: remove all restrictions on spell choice and let the Sorcerer select any spells he wants. In practice, the beginning Sorcerer will go for something like Summon Guardian, which is notably more powerful than the Warrior, but is balanced out by him having to stop and rest every encounter or two.
Another house-rule that I suggest is to make no treasure worth less than 100 gold. Otherwise, the slog through 1st level goes on and on and on at a pace that isn't matched by the other levels.
In sum, this is a great game for getting younger players into the world of dungeon-hacking and I recommend it to anyone with that in mind.