It's amazing how consistently this author comes up with excellent material. Green Gryphon is an adventure module, not too heavy, you can read it cover to cover in one afternoon. Still there is enough background provided to feel comfortable as a gamemaster and well prepared. The setting has mysterious artifacts from ancient times with long forgotten powers and an interesting cast of NPCs. To read about these characters with all their back stories and sometimes dark secrets gives you enough adventure ideas already. But - this being an adventure module - there's of course a whole section dedicated to adventures. They are for low to mid-level PCs and tie in together nicely to form a sort of mini-campaign.
If you are interested in the Shadow World, this could be the perfect way to start and get to know it, because many elements that make this gaming world unique, can be found here. It's also a good way to get a taste of the author's work and style.
[5 of 5 Stars!]