Thunder Rift was one Colin McComb's early projects for TSR, published 1992, before his infamous Complete Book of Elves, of which he's issued a rather humorous apology.
Thunder Rift is a modular campaign setting. You can place Thunder Rift in just about any "standard" D&D world. I remember reading it and wanting to somehow include it in my Greyhawk Campaign. I'd imagined it somewhere in the Abbor-Alz, or maybe the Cairn Hills. But, my players never adventured there.
Thunder Rift derives its name from being a mountain valley where the roar of a waterfall can be heard at least faintly in most places. The rift itself is about 30 miles long, north to south, and 20 miles wide, east to west.
There's actually a lot packed into Thunder Rift's 32 pages. It's meant as a wilderness expansion to the basic D&D Boxed Set published in 1991. Apparently, all of the adventures in the boxed set started characters right at the dungeon. Thunder Rift provides beginning Dungeon Masters an example of what wilderness adventures could entail, but yet not overwhelming them with an entire campaign setting in a boxed set.
It accomplished its aim, in my opinion. It provides short descriptions of wilderness and settlement--enough to get an idea of what's there, but leaving room for the DM to expand as he or she sees fit. In the Gauntlin Forest, for example, elves face a perplexing situation as wild magic plays havoc on the landscape, altering terrain ("Streambeds mysteriously flow into nothingness...") and animals. Meanwhile, the Gloomfens used hold the site of a warrior's academy, but now the academy is in ruins, and the fens themselves are known for their poisonous gases. You even get a fairly comprehensive description (8 or so pages) of the Rift's major city, Melinir, which includes major NPCs, shops, and other places of interest.
Overall, the material is presented well, in a clear, easy-to-read manner, perfect for beginner DMs. You even get a large full-color poster map of the Rift. There's only one major error that I found. Apparently, Melinir is a city of only 200 people
Some might turn their noses up to Thunder Rift's simplicity, but I think its simplicity is its greatest strength. When it comes to campaign settings, any DM really doesn't need to know much more than the area the PCs are exploring. I think fully-developed campaign settings can be overwhelming at times. Colin McComb delivered a mini-campaign setting, complete with a history and plenty of interesting adventuring sites.
Thunder Rift also has some adventure modules written specifically for it. This include Assault on Raven's Ruin, and The Quest for the Silver Sword (and others). Both are worth picking up, at least for their colorful battlemats. The big D&D boxed sets, The Dragon's Den, The Goblin's Lair, and The Haunted Tower if I recall are also set in Thunder Rift, but I am not familiar with them.
I wish I'd gotten more use out of the Thunder Rift. It's a neat little setting.
Presentation: 9 out of 10
Creativity: 7 out of 10
Utility: 8 out of 10
Get this if... you're a beginner DM who doesn't want to bother with designing his or her own region for your games, or if you just want to complete your Basic Dungeons & Dragons collections.
Don't get this if... you have no problem designing your own wilderness areas, complete with its own history, towns, etc, or if you don't like a really generic D&D setting.