Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Impenetrable and turgid to my surprise

I've enjoyed the other five books I read by this author. I found this one so disappointing. I made it through the first four chapters and flicked through the rest. It's dire. He needs to go back to sea or do another follow-on like the Riddle of the Sands/Guns of Navarone ones. Sorry, I'm just really disappointed.