I've just started learning Haskell using the online "Real World Haskell" book, which seems very good so far. But I'd love to hear how that book compares to this site from any experienced Haskell programmers who have used both.

https://github.com/bitemyapp/learnhaskell

I have a general question about Haskell though: I've read in more than one place that writing high-performance Haskell code is not easy for a non-expert to do, and to at times you have to sacrifice conciseness.

While I love the aesthetics of Haskell syntax and higher order functions, I have this paranoia that beautiful code may be slow code.