I mostly like this book! Why the low score? I wanted to call attention to some issues in the book. Lot's of errors. See the errata on the book's page on the Manning site. I noticed cases where variables in examples were inconsistently named. In one chapter, he imports Data.Text.IO as TIO and in another chapter he imports it as TI. Consistency is important when introducing readers who are new to a subject. Overall, it seems the book needed more editing and was maybe rushed. Hopefully these will be corrected in a new edition. There is a discussion forum for the book on Manning's site, however, it seems the author is no longer active on there. I see errors being reported by readers but nobody seems to respond lately. Exercise 2 from chapter 24: > Q24.2 Write a program called capitalize.hs that will take a file as an argument, read > that file, and then rewrite it capitalized. Does he mean to capitalize all the letters of the file name? Just the first letter? The contents of the file? Some of the exercises are underspecified in this way. Thankfully, solutions are provided in the back of the book. In chapter 25 there's a function randomSortSection. One of the exercises is for implementing a similar function with the same type signature called randomReverseBytes. For consistency, it should have been named randomReverseSection. One of the example programs he has you build is for keeping track of an inventory of body parts... Um... yeah, a bit immature at best and macabre or demented at worst. Later the book contains references to the horror author 'H.P Lovecraft', an author of demented and twisted stories. One program you write distorts photos of Lovecraft. The next chapter has references to 'Thomas Ligotti', who makes Lovecraft look like Walt Disney... Seriously messed up stuff. Why would the author choose to propagandize this to potentially young readers? He shouldn't assume that all his readers are immature or emo kids fascinated with bizarre/horror fiction... These juvenile examples may be off-putting for some readers. Many of the other examples were great and were neutral themed. The errata page on Manning's site says the following: "These errors occur in the book's first printing. Unless noted, these corrections have been made to the electronic versions." However, many of the errors still exist in the PDF you download from Manning as well as the live book version on their website. Lesson 35 which demonstrates 'stack' appears to be out of date. Recent versions use 'package.yaml' which the book doesn't mention. The book says to edit 'palindrome-checker.cabal', however this file is generated from 'package.yaml'. It's understandable that a book can become out of date, however, the errata has not been updated, much less the electronic versions of the book. In Lesson 40, in the following: data NOAAResult = NOAAResult { uid :: Data.Text.Text, mindate :: Data.Text.Text, maxdate :: Data.Text.Text, name :: Data.Text.Text, datacoverage :: Int, result_id :: Data.Text.Text } deriving Show it seems that `datacoverage` should be a `Double`. At least when I retrieved the data from NOAA, it had some float values for this field. The answer in the back of the book for Q41.1 doesn't insert a value for the 'last returned' day. So when you add a tool using the suggested function, the field for 'last returned' is NULL. I've attached a screenshot of a version which resolves this by using the current day. If the quality issues are resolved in a future version, I'd likely give this book a 4 out of 5.