The author of DDD has openly admitted in a podcast that his book is essentially a scam.

He wanted to write a book about Clojure, but the publisher said that there was too little interest. So he "tricked the readership into reading a book which is about Clojure without saying that it is about Clojure". I'm paraphrasing, but that is the genuine gist of what he said (much to the non-amusement of the interviewer who must have felt deceived as well).

Source: https://changelog.com/podcast/522

I even read this stupid book because there was a hype at work and it is so full of strawman arguments it made me furious.