Did Marvel invent it? I thought they copied it off of Warner Bros/Time-Warner and how they'd been handling the DC Comics properties since they acquired them in the late 60s. (But of course, Marvel is the master of this kind of brand management strategy).
This doesn't surprise me at all. D&D novels took up several shelves even in my tiny local independent bookstore. In a B. Dalton or Waldenbooks, it was entire sections of shelves. And it moved! Until it didn't. The intriguing worlds explored with strong voices began to be diluted by many different authors with varying levels of writing ability and/or knowledge of the world they were writing in. The firehose approach flooded the market, who knew?
But the Dark Sun novels, the saga of Prism Pentad, altered the metaplot, killing important big fishes, and now we don't know if the future DS will continue the metaplot or this will be rebooted again to can add more changes, for example PC races from later editions.
And the "primal-punk" look is one of the marks of identity, but this needs a lot of work by the artists.