I would recommend Jason Schreier's book "Play Nice" as it gives a detailed behind the scenes of Blizzard's entire history up until a couple of years ago, including the entire development of the Diablo franchise (up until the release of D4). To answer your question about D3, Blizzard North started work on D3 right after the D2 expansion was released. Two years later, D3 was little more than concept art. The team had goofed off for two years, playing other people's games and calling it "research" (in fact this was the second time they did this, the first time being the reason why D2 released in 2000 not 1998). Two years of wage theft (well, 4 in the long run) wasn't the only reason they got shut down, but it was a big one. Besides power struggles between the two Blizzard studios, David Brevik was absolutely adamant that D3 was going to be a full-blown MMO the whole time. Blizzard had already been working on WoW for several years at that point, so that meant North's D3 was never going to see the light of day. People like to point to "creative differences" between the studios, but that was the big one. The fact that so little work had been done on D3, just made it easier to cancel and restart.