Disclosure: I have written a number of products for the Dungeon Crawl Classics game, including some for Goodman Games.
I have written about this product before, and my general impression remains unchanged.
Physically, this is a beautiful book. I currently own three copies of the rules - a 1st print, a wizard cover variant, and a 4th printing soft cover. The art in this tome is amazing; you should be able to come up with dozens of adventure ideas merely by flipping through the pages and looking at the illustrations. I was going to list some of my favorites, but looking through the book, I think that is probably impossible. There is just too much good stuff here.
In my opinion, the best role-playing game book ever produced was the 1st Edition Advanced Dungeons & Dragons Dungeon Master's Guide by Gary Gygax. This is a close second, and sits proudly on the same shelf.
If you are interested in the rules, but have yet to play (or purchase) the game, the Spellburn podcast gives a rundown of many of DCC's unique aspects. An introduction to Dungeon Crawl Classics can be found here. Other topics include 0-level funnels, classes (ex. clerics, thieves, wizards, and halflings), the magic system (mercurial magic and spell duels), mighty deeds of arms, monsters, magic items, dragons, and demons.
The 1st to 3rd printings contained two adventures, The Portal Under the Stars by Joseph Goodman and The Infernal Crucible of Sezrekan the Mad by Harley Stroh. Both adventures were reprinted from the DCC Free RPG Day Adventure Starter. The 4th printing replaces The Infernal Crucible of Sezrekan the Mad with another Harley Stroh adventure, The Abbot of the Woods. This last is a rather nasty adventure for characters of level 1 to 3, and which may easily see party attrition. Or extinction.
Obviously, I am a fan.
Get It Here.