This achievement is not particularly difficult and I am certain many will achieve it without trying. Historical facts can be accessed while playing by pressing "Y" (or by going to the Historical Facts tab in the pause menu). Here you will be treated to four or five pictures per level section accompanied by captions, informing you about the war. These vary from information about troop transport trains, the Battle of Marne etc. The ones you have not yet read will feature a white exclamation point flashing in a red hexagon. Simply scroll over them so the hexagon disappears. This counts as having been read.
It should not take long. I have yet to finish Chapter 1 and have already read eight.
*Addendum- The game will even prompt you on occasion with an icon of a book pile and the red hexagon in the upper right of the screen. This indicates new facts to read.
*A2 by Crayon Taster "If anyone else finished the game without getting this achievement I wanted to mention that you don't even need to start each mission again to get this achievement. You can simply go to "Chapters & Collectibles" from the main menu.
Select the chapter, highlight the mission and instead of starting the mission select Collectibles (press Y). I think it defaults to the items, but if you push RB you can read all the historical facts from that menu. It's a breeze to go through to fill in any facts you may have missed. Even if you didn't read any of them during your playthrough you could easily get all 30 in a maybe 10 seconds."