[mjepronk]

I like the book Domain Driven Design by Eric Evans.

Also, pure functional programming and immutability have greatly influenced my design even in languages other than Haskell (my main language is Python).

Eric Evans also stresses the importance of immutability of what he calls Value Objects.

[sdevonoes]

I think the Evan's book about DDD is the worst by far. The one from Vaughn Vernon is better imho (more practical without losing the theoretical aspect).

[Supermancho]

Working with languages that force a lot of immutability (Erlang, Haskell, etc) will change how you think, for sure.