These games are an adaptation of a series of gamebooks, i.e. paper CYOA books. They must have been absolutely incredible, because this game is rich in detail and options. The game is played on a large 3d-map which you place a DND miniature-type figure on, moving it around to indicate your choice of route (between 2 or 3 options at a time).
You have stamina, gold, rations, spells, etc. The spells are cast by using up some stamina and selecting 3-letter words out of a cloud of letters. The available words differ quite a bit from situation to situation.
The combat system involves guessing a number at the same time as your opponent, trying to beat them without using up too much of your strength. It ends up being a sort of dance between attack and defend.
There are numerous side quests; the main quest can be finished extremely quickly, while one side quest took up an hour of gameplay by itself.
Highly, highly recommended.