These are $5 for a reason. http://www.reddit.com/r/haskell/comments/1rj2jq/book_haskell...
They seem to exhibit the same behavior as online content-farms. Shame we don't have a real-life Panda update to squash subpar books.
I dont have enough packt titles to evaluate their general quality, but at least I found their early solr books useful(it was also the only book on solr back then, so not much choice :)