I don't think it is worth the pain of writing a full-blown review for Eureka and Masks. Trolling the net you will stumble upon tons of enthusiastic opinions about both products. Here is mine!
I'll cut is short. If you fall in one of following descriptions:
- game master (or GM wannabe)
- illustrator/visual artist (yep, I'm serious)
then, simply put, buy this bundle. Maybe you still don't know but you need both the books. Dot.
If you don't, keep away! Reading such material could spoil years of gameplay, even if your master doesn't use it. Believe me!
These are that kind of books that should be kept right behind GM screen (or in a writer secret drawer) to express their full potential.
With Crimson Exodus, this is the best product I've ever bought on this site.