This review is for the digest sized physical copy. I'll break the review into two parts: the book and its layout, and the content.
I received the book as a Kickstarter backer and chose to read the print version instead of the PDF. It may be that these comments do not apply to the PDF. First, i thought the type was a bit small; readable, but I would have liked it larger. Second, one of the tables had small type combined with a crinkled paper background that made it unreadable. I was disappointed with that and do not understand the decision to use that background for the table.
The main reason I backed the Kickstarter was to see the Savage Worlds rules for flying mounts. But after reading the book, those rules are not what I like best. In fact, I consider the rules a minor part of what makes this a good book. I most enjoyed the historical details and how the world of Kaiser's Gate differs from our own. A lot of good information is contained in a compact space. I never found the historical information boring or tedious, and wish there had been more. In particular, I liked the references to Serbia, which often seems forgotten in discussions of WWI. Even better, the historical information is presented in a way that naturally suggests adventures to the GM; a number of adventure hooks are included after each section.
In summary, a well done supplement with good historical and rules information. The print version could use better graphic design.