I think the book tried to show more how to use some language features with some examples that can be applied in the real world. I agree with you that the book missed the bigger picture and how to use Haskell in modeling abstractions and designing modular and extensible systems.

I think Haskell is a great language but still it will be some time for it to gain wider use in the industry.

Me personally came to understand the language more through articles and blogs than through this book.

Do you have links to articles or sites about Haskell being applied in enterprise development?

I enjoyed very much this online book that you probably already know about but share it here anyway:

http://learnyouahaskell.com/chapters

Cheers,

Karel