One of the last of the first edition AD&D rule books. While I grew steadily less impressed with TSR's releases over the years, the DSG was something of a breath of fresh air. Like its contemporary, the Wilderness Survival Guide, it offered some new wilderness survival skills, and advice for the DM for making terrain an interesting part of a challenging adventure. Its crowning feature, in my opinion, was the explicit introduction of the idea of the Underdark. At a time when the trend was toward longer and more involved modules, and even trilogies of long involved modules, with little if any action taking place in hack-n-slay dungeon crawls, the Underdark concept was a return to the dungeon crawl on a grand scale.