After HeroQuest and Advanced HeroQuest there's Warhammer Quest (WHQ), published by Games Workshop (GW), and it really is more advanced than those other two dungeon crawl games.

So what's a dungeon crawl game, exactly? In a nutshell, these are a kind of simple roleplaying system. Usually, it involves 4 fantasy heroes venturing forth into a dungeon to kill monsters, solve a quest and collect treasures. A Game Master might be needed, just like for regular roleplaying games, or not. Case in point: you can play Warhammer Quest without a Game Master.

The Box
The first thing you'll notice when opening the box is how much material it's got: dozens of miniatures (4 heroes, 3 minotaurs, 12 giant spiders, 12 giant rats, 12 snotlings, 12 giant bats, 6 orc warriors, 6 orc archers, 6 goblin archers, 6 goblin spearmen, 12 skaven, and 12 plastic doorways to connect the floor tiles), floor tiles (11 corridors including t-junctions and corners, 6 small rooms, and 5 quest rooms), dozens of markers (spell effects, cave-in, portcullis, power tokens, and more), various cards (dungeon deck, treasure deck, event deck, spell deck, warrior cards, equipment cards, blank event cards), many dice (in two sizes; the smaller are used to track the damage the monsters have taken), an adventure record pad, and 3 books (rule (32 pages), adventure (16 pages) and roleplay book (192 pages)) - you'll have a hard time placing all of this back into the box! That's what I call bang for the buck.

The rules
Before play can start, some preparations are necessary. First and foremost, the Dungeon Deck needs to be assembled. For that you first draw one of the 5 quest rooms, and roll a d6. This roll determines the quest the characters are on, and each quest room has its own 6 quests.
Then, the quest room card you've drawn is shuffled with 6 other (non-quest) Dungeon Cards. Another 6 cards are dealt on top of these. That way, the quest room will be the 7th to 13th card drawn.
Now each player chooses a warrior (the WHQ term for the player characters), rolls 1 d6 and adds a certain modifier depending on the warrior - the result is the starting Wounds of that warrior.

On to the rules. The basic rules, described in the rule book, are pretty straight forward.
First, it details what the warriors are made of, and what the basic stats are: Wounds (W; if Wounds reach 0, your warrior is dead), Movement (M; how many squares your warrior can move per turn - usually 4), Weapon Skill (WS; the higher this number, the easier you can hit other creatures in melee, and the harder you are to hit in return), Ballistic Skill (BS; how good you are at ranged combat), Strength (S; higher number means more damage dealt), Toughness (T; higher number means less damage taken), Initiative (I; used to determine in what order the warriors act), and Attacks (A; how many times you can try to hit opponents per round).

There are four basic character types in the basic game: the Barbarian (melee specialist; may rage for extra attack), the Dwarf (durable melee specialist), the Elf (mobile ranged specialist) and the Wizard (a spellcaster, obviously). All warriors have different stats - the dwarf has the highest WS, the elf has the highest BS, and so on - and each has his own special abilities. For instance, the Barbarian will try to rage in combat, and that grants him an extra attack - but the rage may backfire and hurt the other warriors; the Elf can always break away from melee (others warriors need to roll a dice); the Wizard can cast spells.

While we're talking about spellcasting: every round (where all warriors act in order of Initiative) begins with the power roll. The player of the Wizard rolls a d6, and that result plus his level is the number of power points he may spend in this round to cast spells. Each spell costs between 1 and 12 power points - the better a spell is, the more power points it costs.

But the power roll serves another role too. If the dice comes up as a 1, a random encounter occurs - draw a card from the Encounter Deck. Additionally, on a roll of 1 the Wizard may not add his level to roll, so he'll be at a meagre 1 power point - not enough to cast most spells.

After the power roll, all characters act in turn. If the leader - the warrior holding the lantern - ends his move at a previously unexplored tile, a card is drawn from the Dungeon Deck. If it's a room, an encounter will occur - draw a card from the Encounter Deck.

Combat is pretty easy: you try to hit your opponent by consulting your to-hit chart (depending on your WS), and rolling a d6. If you roll high enough, you hit.
For instance, the Barbarians WS is 3. He'll hit opponents with a WS of 1 on a roll of 2+, with a WS of 2 on a 3+, with WS 3-6 on a 4+, with a WS of 7-9 on a 5+, and with a WS of 10 on a 6+.
If you hit, you roll for damage. Roll a d6 (some weapons and some opponents may roll more than one d6) and add your S, then subtract the opponent's T - the result is the number of Wounds that opponents looses. If he drops to 0 W, he's dead - that's called a death-blow, and the warrior may immediately attack another opponent adjacent to the first one as cleaves thru them. A warrior can continue a death-blow until there aren't any opponents left in reach, or if he fails to kill an opponent.

Spellcasting works a little strange - the Wizard can cast a spell at any time, even during the monster's phase. As long as he's got enough power points to do it, he can even cast more than one spell per round. Perhaps the most important spells are healing spells - without these the warriors are prone to die rather quickly. Because a Wizard can cast spells at any time, he could still heal a warrior that just reached 0 Wounds.
Now remember what I said about random encounters: the Wizard is at 1 power point in the first round of the random encounter - that means very few healing power, if any! For that reason, random encounters are way more dangerous than room encounters.
But there's hope: the Wizard starts each quest with a certain number of power tokens (depending on his level) - he can use each token once per quest as an additional power point.

After the warriors have defeated all monsters, they may draw one treasure card. Additionally, they collect gold pieces depending on the difficulty of each defeated monster - by the rules, the warrior who killed the monster gets all the gold for it (I'd advice to house rule this, though).
Not all encounters are combat encounters - events may occur too. But most events won't grant the party any treasure.

The quest room holds a very tough encounter, two or three times as tough as any other encounter. If the warriors are victorious, they've solved the quest and won the game.

Character development, detailed in the roleplay book, is rather simple - once you've collected enough gold (there's no such thing as experience points in WHQ - you simply pay for training) all you do is roll a dice and add the result to your hit points, and now and again you'll add a new special ability (the wizard, on the other hand, gets access to more spells each level).
Furthermore, there's a fifth warrior type, the Trollslayer, which can be chosen in place of any of the four basic adventurers (but I'd advice not to adventure without a Wizard, or else the party will be short on healing).
Warriors levels range from 1 to 10, and the roleplay book has tons of monsters and treasures to make high-level play interesting and challenging. Note that you can't use the Encounter Cards for any level above 1, you'll rather have to use the encounter tables detailed in the roleplaying book instead.

The roleplaying book has many, many more rules. For instance, there's a table for events when the warriors travel from the dungeon to the city.

Opinion and conclusion
This game is fun, pure and simple. It's easy to learn and runs pretty quickly, both during and after combat.
Most of the monsters are prone to die by the dozens, and that's certainly one of the appeals of WHQ.
While the encounter cards and tables that come with a game have a somewhat rag-tag feel to them, it's easy to design your own encounter tables, using only the various orcs and goblins, for instance. The two WHQ expansions do exactly that (among other things), one for orcs and the other for undead.
I'd recommend this game to anybody with their own miniature collection (preferably GW minis), or with a preference for dungeon crawls, or ideally both.