At the moment I do not own any of the 4e books other than the Red Box which I bought mostly for nostalgia.
I know that since they were printed there have been a lot of errata to the core books of 4e and that the newer Essentials books include the rules compendium etc.
What I'm curious about is what would be the minimum set (as of early 2011) which would make for a solid core for a gaming group who want to play 4e? I would likely include a D&D Insider subscription for at least the DM? But what else would you suggest?
Clearly a group could use any subset of the books they want - but what would combine to make the best minimum set for a fun game. (miniatures and dungeon tiles are perhaps a separate question but with the essentials perhaps those tiles and counters would be useful?)