From Googling around a bit I've gotten the impression that:
- The Light Novels (LNs) are the source material
- The "Progressive" novels (PNs) expand upon the source material
- The Manga was adapted from the source and contains no new content
- The Anime was adapted from the source and contains no new content
Though I'm not certain about any of those.
Assuming I'm correct, I'm unclear in what order the LNs and PNs should be read. For instance, I would expect it to flow best if I read the PN 'filler' that takes place in SAO before moving beyond Aincrad in the LNs. Assuming I'm incorrect, I have no idea in what order to intersperse each of the types of written materials.
In what order should I read written materials to cover all available relevant information in appropriate chronological order without spoilers?
So far I have read nothing, and watched the first two anime seasons plus the movie (all dubbed).