This is a departure from the rest of the Dungeon Crawl Classics line in that there's no plot, no adventure. Very simply, it's jam-packed with old school style floorplans for all manner of places, ready for you to build your own encounters and whole adventures around.
If you have an idea floating around, but lack the time (or the talent) to draw out where that idea takes place, leaf through these pages and pick out a location. Rather neatly, there are 120 modular map segments that can be combined in all manner of ways (hence 'geomorphs'). These segments include mazes, dungeons, underdeep caverns, monstrous lairs, castles, ruins, halls, and many other intriguing places to explore.
Each page has four segments, and each segment has eight entrances/exits which match up with any other segment - even if you turn them around. There's no set 'up' and 'down', you decide. They are all provided with a square grid, but it's up to you what the scale is, although 1 square = 5 or 10 feet is recommended... unless you want a really massive cavern or chamber, that is. There are some blank gridded segments as well in case you get creative and want to add your own designs.
If you don't like anything, change it - a black 'magic marker' is the best tool. Print or photocopy a segment that's fairly close to what you want, scribble on it and photocopy again. Or import into a graphics program if you prefer. Similar techniques can be used to produce handouts of treasure maps, stolen plans of lairs or whatever which may not be a completely faithful reproduction of the real version in your game file!
A useful tool when you are partway between wanting to use a prepared adventure or develop your own. Caves, castles, hallways, lairs, places with deep chasms or rivers running through them... just about anywhere you might choose to delve.