If it’s a recent book, say not more than 8-7 years, there is a 35% chance you can find it online in .pdf format for free. I kidd you not. You could almost be asking in general for history book recommendations, as chances are like I said you’ll be able to find 35% of them (the recent ones).
I find I have most success at ebookee but there are many sites like that, where you can look for books for free, mainly in pdf. Some may be found on Scribd. And you can just google. And also torrents. There is a gigantic history book torrent, it has 3GB worth of ebooks (it’s not .pdf, but it’s free). I know just a few of them, but I’ve downloaded two dozen from there to check out when time allows. (Also there is Russia Against Napoleon from Dominic Lieven in that torrent which is just incredible.)
Finally I have dozens of history pdf books, most of which I can recommend, part of my digital library. It’s a little bit bigger now than what you see in the link, but stil fundamentaly alike, somewhat East Europe-centered. If something like that sparks you interest say so and I can upload some of them for you to download. (I’d upload all of them in a package somewhere just for anyone to DL without being prompted, but unfortunately I’m currently on an UMTS line so I can’t have too much traffic.)