how to read a chess book?

is it best to setup a real board and play the move and learn to understand the explanation? also, there is a lot of variation lines in between the actual game moves played in books....do i have to play every single variation move onto my board as well?

It's best to set up TWO real boards. A larger one to play out the games on and for examining the variations, and a smaller one to hold the game position while you are playing out a possible continuation on the larger one.

Example: Use the larger board to follow the game out to a critical point, then copy the position onto the smaller board while you explore the various possible combinations on the larger board. When you feel that you now understand the position, reset the larger board to the position that you have "saved" on the smaller board, and continue playing out the game. 

https://www.chess.com/forum/view/chess-equipment/how-to-read-chess-books-1

Depends on the book. For opening books, one can see this sort of advice:

"... If the book contains illustrative games, it is worth playing these over first ..." - GM John Nunn (2006)

"The way I suggest you study this book is to play through the main games once, relatively quickly, and then start playing the variation in actual games. Playing an opening in real games is of vital importance - without this kind of live practice it is impossible to get a 'feel' for the kind of game it leads to. There is time enough later for involvement with the details, after playing your games it is good to look up the line." - GM Nigel Davies (2005)

thanks

I second blueemu's advice. Two boards can be super helpful. Of course it depends on what sort of book you're studying, but having such an easy way of checking the variations and then going back to the original position is very useful. In an opening book, for example, the variation is probably included for a good reason so it's worth going over. You can do it first time you go through a game, or play the main line and then go back to go over the game a second time looking at the variations. Basically, whatever works for you - but using a board is a great idea (especially if you plan to play other people in person at a tournament or club, there's something useful about using a board and not relying on the computer only)