I always suggest the person pick one opening and study and learn it - not just the expected moves, but why those moves are played. It doesn't really matter which opening, but I like the Ruy since it's more directly fundamental chess principals.
As far as just getting better, tactics and not hanging pieces is good.
Thanks Sandal, Last few days I'm studying one of the openings and realized that analysis of certain moves and pattern helped me in similar positions. I could see some variety of moves much faster and in which direction to head to;
I have not read the book, but I would guess that it has value for many active chess players. What about someone who is "not even a player" and "using chess to work on concentration" "As well as other purposes"? I would not venture to guess.
Your opinion is valuable to me, regardless.
I have no opinion on what would suit your purposes.
("... I apply chess learning to life in some way or other. Ofcourse I enjoy the learning too. But I apply it learning to think a few moves ahead. Also, by learning an overview of chess I learn to see the whole board therefore reinforce visualisation. …" - joseph1000000)
Perhaps a good idea for you to go to the Everyman site and try to examine the sample that is currently available there.
I meant your opinion about the book. ...
It does not make sense to me to have an opinion about a book without consideration of the reader. A book can be good for one reader and not good for another.