Runequest 2nd edition was, as previously established, my second go-to roleplaying game in my (and the hobby’s) early days of roleplaying. The house system used for RQ came to be known as Basic Roleplaying or BRP. The earliest instance of the BRP rules on their own was a 16-page booklet in the Worlds of Wonder box set. This and the three setting specific world books established that BRP could serve as a game engine for a wide range of genres.
Skip forward twenty years
Thanks to various events, Chaosium lost the rights to Runequest. They still owned Basic Roleplaying, however, and this, the 2008 Big Gold Book, is the most recent attempt to distill into one volume enough essentials of the system to serve as a generic game system, from fantasy to science fiction, from mystery to superhero.
BRP mechanics are straight-forward and suit settings where characters should be comparatively fragile. The essentials are easy to convey to new players, although the ease with which characters die or go mad should perhaps be left as a delightful surprise.
As it happens, Chaosium regained the rights to Runequest, which means this edition of BRP is somewhat surplus to their needs.. PDFs of the main book and various supplement are available but currently physical books are not available. This may change in the future. In any case, another streamlined edition of BRP and various BRP-based games are in the offing.
As it happens, I have a use for such a flexible system. The nostalgia aspect does not hurt.
(I’m joking. I’ll kick ideas around, and hunt down various supplements to see if they have the elements I want but I never actually run anything)