Fantasy fiction has been greatly influenced by Dungeons &Dragons, including several book series based on D&D campaigns. But very few novels have dealt with the dungeon exploration aspect of it, where characters explore underground ruins and encounter monsters, traps, and treasure. Even actual D&D novels tend to downplay it.
But this novel is focused pretty much entirely on dungeon exploration. Two very experienced adventurers, a master thief and a powerful wizard end up exploring a cave, which turns out to be much more than that, a large dungeon complex. So they explore, partly out of curiosity, partly to look for loot.
If you've ever played D&D, you will recognize many, many D&Disms. From the abilities of the thief character to most of the spells used by the wizard
If it were just dungeon exploration, it might get boring, but the two characters have a pretty good repartee between each other. Maybe not Fafhrd and the Grey Mouser, but often funny.
Only downside is the ending, which is awfully abrupt