I recently picked up a beta copy of Programming Erlang: Software for a Concurrent World to go along with my (paper) copy of Programming in Haskell. I figured if I had both books, I could make quick runs through them as I try to decide between Haskell and Erlang as the FP language I'm going to focus on this summer. What follows isn't really a review of either book, just a few first impressions.
Programming Erlang: Software for a Concurrent World looks like to be a very accessible book, that also goes into enough depth to be worthwhile. The version I got yesterday had 279 pages in the PDF, but an update was released today and my new copy hasn't found it's way here yet. I like what I've read of Joe Armstrong's writing and examples, and have caught on quickly to the initial concepts.
Programming in Haskell surprised me by being really small, only 171 pages (including the index). It on the scale of 'The C Programming Language', and so far it reminds me a lot of that book. I have to admit though, that I've always been put off by the seeming need of Haskell writers to use 'special Haskell characters' in their text, Programming Haskell even includes a table of 15 such symbols and how to represent them in ASCII. Bleargh!
So far, I'm leaning towards Erlang (mostly because of concurrency), but I'm not going to make up my mind for a while yet — too many other deadlines I need to deal with right now. As I get closer to the summer, I'll let you know which way I decide to go. (I'll also get real reviews of the two books up fairly soon.)