Who's the best chess writer in your opinion?

A great chessplayer is not necessarily a great chess book writer. 

Silman

Silman

It is tough to decide.

I guess the best ghost writer is ghost of pushwood though.

Mark Dvoretsky.

Yusupov and Silman have probably had the most positive impact on my game for now. Dvoretsky may join them at some point.

Not Mikhail Shereshevsky ?  Can you elaborate a bit why Mark ? 

Kasparov ?  Come on .... I don't think so , not at all perhaps,  he's much better player after all.

No one mentioned Max Euwe, Mikhail Shereshevsky,  Boris Gelfand I'm shocked 

Fixed that for you.

irving chernev, " Combinations the heart of chess"

P.S, I  read a few books only, but I practiced/ played together with dozen of engines.

Axel Smith's books are pretty good. I highly recommend Pump Up Your Rating.

I'll probably get lambasted for saying so, but I completely disagree with the general consensus that Nimzowitsch is a good writer. I did not get on with My System at all, he's so full of himself.

The Kasparov books (I have the On My Predecessors series) are great, but they aren't amazingly written. Some of it is very cut and dry, long variations etc. Informative and interesting, yes. Well written... not as much.

Heisman, no one even mentions him! His advice is simple and direct--safety first! If you move safely and don't fritter away your pieces your ratings will improve! He makes this point in his writings and his videos. 

Rowson

He has authored two great books, for sure. But just two.

Mark Dvoretsky has authored plenty of great books, and his chess lectures were used by other authors, e.g. Shereshevsky.

What about Boris Gelfand? 

I'm currently going through the blue positions in Dvoretsky's Endgame Manual and I have to say that even at my low level, I am learning plenty and getting a lot out of it. I'm sure if I was higher level, it would be even more beneficial.

If not Mark , who would be your second pick ?