A new biome, with new enemies, new weapons and armor, new magic, fishing expanded, more building parts, more furniture and cosmetic stuff, new resources, new food. Pretty much expanding on everything.

The game was already worth it, and this update has plenty to offer for those that already loved what was there. And there's still more to come as the game continues along in early access. In before the "Updates are too slow!" crowd start crying

It's a great game, but do your due diligence. Check out gameplay, maybe watch some streams, ask questions. Know what you're buying before you put your money down.