I have a feeling that all four of these books are going to be asked about based on their recent appearance on eBay. Back in 2015 we Kickstarted RuneQuest Classic, which ended up raising over $200,000 from 2176 backers. The kickstarter brought in a lot of money for the company, which was badly needed at the time.
The top tier $1000 HIGH PRIEST backer level offered four special books (shown above) as part of its rewards. Each is about 256 pages long:
The RuneQuest Playtest Manuscript book – this is a 250+ page hardcover book created from high resolution scans of the original RQ1 playtest manuscript. This manuscript is the only known set of playtest notes in existence which were lovingly kept in a binder for the last 40 years. The The RuneQuest Playtest Manuscript book includes newly written introductory essays by Steve Perrin and Greg Stafford.
-- Sven's original RQ1 playtest manuscript --
Books 2-4 in this set are collections of fragments of incomplete projects. In general, there a lot of handwritten pages, maps, and similar. Few sections from the outlined contents are even close to complete, and whole sections were never written (or lost). We did a podcast about their contents.
-- notes about the Dragon Pass region --
The West, Sorcery, and Arkat – This is a collection of material that would have formed part of the "The Brithini/Mortal Lords", which I detail on page 37 of the Meints Index to Glorantha 3rd Edition. It contains lots semi-related bits of material, and is the least coherent volume in this series.
Dragon Pass and the Wilds – is a collection of material being worked on for a campaign spanning most of Dragon Pass: Grasslands, Black Horse Country, Wint
ertop, Upland Marsh, and so on. Lots of Towers to loot, plus a fair bit of info on Dragonewts and Elves.
Encyclopedia Glorantha – This is "The Hero Wars" manuscript from 1980. It was meant cover all the Lunar Wanes, a history of Dragon Pass, the Hero Wars, and more.