As an Airbus A320 captain myself with over 30 years in military and commercial aviation, I personally find such behaviour extremely non-professional and akin to poor airmanship.
What a pompous statement!! I hate to think what 126807 is like to fly with.
Personally I think reading is good for mental health. So is having a chat with your colleague. It makes for a more pleasant working environment. Freedom to relax a bit and have a chat if you want to or read a book/paper is good. It means when something concerns you, you are more likely to become vocal about it if you're relaxed and the skipper is approachable. Jokes and anecdotes are good for crm too.
Who likes doing a crossword or a sudoku in the cruise?