Curse of Strahd is a great adventure, but a difficult campaign to DM. I've drawn on the great supplimental material from MandyMod and /u/DragnaCarta already, and Wyatt Trull's Companion series is another great resource.

I found this chapter (Argynvostholt) particularly useful. As originally written, the revenants are faceless melee challengers. Giving each one a distinct personality and motivation fleshes out the story very effectively. Also, Trull suggests an alternative ending that fixes the obvious plot hole in the original.

This is a definite pickup, and I look forward to the rest of the series.