Which of the greatest chess players were the best chess book authors?

By greatest I mean undisputed world champions or should have beens like Keres

Is there uniformity here or is the quality of writing proportional to their prowess as a chess player. Interested to hear people's thoughts on this

Quality of writing doesn't appear to be correlated with prowess or rating. I guess it's simply that some people can write well, entertainingly and/or instructively and some can't.

Timman, without any doubt.

Timman's a great choice, but Tal is an even better choice. Tal's journalistic style made Life and Games one of the classics of chess literature. David Bronstein also deserves mention, especially for his Zurich 1953.

Aron Nimzowitsch was ranked in the top five in the world for over a decade. He should aslo be considered.

The only reason Nimzowitsch didn't play for the world championship against Lasker was a lack of money. Though I do wonder if Lasker may have ducked him anyway. There's some evidence that he set extraordinarly high fees for his challengers in part to avoid playing them.

If Nimzo qualifies as a "great" chess player, then the discussion may be over. He is certainly the most influential writer in the history of the game, and I would rank him as probably the best chess author.

Since you laid out the condition "world champion level", the list is very easy to find. Tal, Bronstein, Keres, Fischer, Kasparov all come to mind. Best author is a matter of taste and what you look for in the book, is it the historic perspective, or psychological anecdote or is it the instructive game annotation? 

Can't believe noone has mentioned Euwe !?   

Ok, you give some great examples but don't forget Timman wrote a LOT of books and published LOADS of articles and a number of brilliant endgame studies. And all of them at absolute top level quality.

Yet.

Tal and Larsen.

Euwe's definitely a good choice. I was thinking also of books by Lasker, Capa, and Alekhin. I never liked either Lasker or Capa for their writing style. Alekhin embellished his own game scores, but I learned a great deal from his commentary.

My 60 Memorable Games is an absolute classic, but apparently Larry Evans wrote most of it. Kasparov's books are incredible for the level of their analysis, but the writing is a bit muddled in places and he doesn't cite his many sources. Karpov's books are very much hit-and-miss. 

So, for me, among world champions (Keres doesn't qualify), the two best are probably Tal (clear first) and Euwe.

The OP said ---> "By greatest I mean undisputed world champions or should have beens like Keres"

So he does qualify. And so does Timman

Off the top of my head:

Lasker - Laskers Manual of Chess

Nimzovich - My System

Capablanca - Any of his books

Euwe - Chess Master vs. Chess Amateur

Fine - Basic Chess Endings

Purdy - All of his books

Timman's Art of Chess Analysis is one of my favorite books. I loved it so much I had to buy the new edition when it came out because my first copy was falling apart. I also have Timman's Selected Games. That isn't nearly as good. It's very good, but not in the same class. But Timman wasn't ever close to being the World's best player. Same goes for Larsen, Keres, Taimanov, Speelman, Hubner....

At least Bronstein drew his World Championship match. 

Fine goes down as one of the worst writers among elite players! Read Psychology of Chess some time.

Do you believe that either Keres or Timman "should have been" undisputed world champion? If so, in what year?

Two of my favorites are by Tal , his life and games and the Botvinnik match of 1960 ?  that Tal won .  The two books that Euwe wrote on the middle game helped me tremendously and are my favorite of his .  My favorite is My System by Nimzovich as I made the biggest rating jump ( in 1 year ) after studying this book ... 300 points !  Unfortunately his Chess Praxis didnt produce a similar jump ... I dont have a single book by Larsen but want to get one ... which of his is recognized as his best book ? 

Keres won AVRO 1938, widely considered to be the strongest tournament ever held at the time, so he can't have been all that far away from being the best player in the world. At least for example Euwe never won a tournament at that level. Larsen won the first Chess Oscar for the world's best player back in 1967, but that was a few years before the 0-6 made him seen as never having been anywhere close to such a position.

I agree that Timman doesnt qualify but Keres .... maybe he does , he certainly has a better claim than Timman . 

Everything Larsen has written is enormously entertaining, from simple Good Move Guide books to analysis of his own games. This one is worth a closer look in a few months:

http://www.amazon.com/Bent-Larsens-Best-Games-Fighting/dp/9056914685/ref=sr_1_1?ie=UTF8&qid=1402076546&sr=8-1&keywords=bent+larsen+chess

Excuse me? Are you drunk??

He was in the top 10 for like 20 years or so, I think.

Did a quick check, might be missing some.

In 1982 #2 behind karpov

In Jan. 1985 #3 behind Kasparov and Karpov

In Juli 1985 #3 behind Karpov and Kasparov

In 1986 #6

In 1988 #3 behind Kasparov and Karpov

In 1990 #5

Played a world championship match vs. Karpov