From the introduction:
Welcome to The Drow War, Book One: The Gathering Storm!
This is a linked series of three 256 page books. Each one contains a single epic story broken into ten parts, thus making 30 discrete adventures in total, all tied in to one overarching saga.
The adventures are structured to take the characters concerned from first level to thirtieth level. Each book covers a span of ten levels, meaning that every adventure will (if completed successfully) advance the characters by approximately one level of experience. Naturally, this outcome is not guaranteed, nor is the progress going to be one long grind!
The story of the Drow War begins with a mysterious summoning to a stone circle in the north of the island of Chillhame, close to a fishing village that is about the most unremarkable place on earth. As the Player Characters explore their surroundings and learn more about why they have been brought here, helping the local villagers and finding out about ancient legends, they are abruptly plunged into a burgeoning war. A long-exiled evil has been brooding beneath Chillhame and now its armies seek to march on the surface.