Haven't been on these boards in a long time, and going through a few threads today, I see a lot of things like:
- updating monsters to MM3 standards
- {this rule} revised by {this book}
I have been DMing with just my original 4E books, happily churning along in ignorance. Are they obsolete now? Do I need to pick up this Rules Compendium Book or DM's Kit in order to keep up?
No, but you need to look at some errata. There's a combined document, although you only really need to look at errata for PH1, DMG1 and DMG2 (even if you don't have that last product).
IMO, the most important issues to deal with are monster stats and skill DCs by level (generally lower). I've noticed my PCs now either beat skill checks or narrowly fail them instead of horribly failing them like they used to. (They failed their last important one by literally 1 point, which forced them into a nasty combat encounter.)
Note that some monster designs have undergone considerable changes; this especially applies to paragon and higher level monsters, elites, solos and orcs. (Arson, Murder and Jaywalking.
) Note that dragons have become some of the best-designed monsters in the game. The ones in the MM1 look good, but they're not
Some slightly less important issues are the race errata (for instance, dwarves get a choice between boosting Wis and Strength, so dwarven fighters are good instead of wimpy; half-elves can choose between a bonus to Con or Wisdom, the latter actually results in a weaker character, but said bonus might be worth it for RP reasons; tiefling's racial powers are a bit better, etc).
There will also be chatter about Expertise feats, Essentials classes, and what have you. You don't need that stuff, although I'll plug the Essentials Knight and Thief classes as being superior to their PH1 version (both, especially the Knight, are better at doing their job), and the Essentials Mage is neat, if a bit limiting.
