So I knot a LOT of people downloading ebooks on illegal sites. With that they could be downloading viruses too, so I strongly recommend you check out Project Guternberg, cause it's legit and you can download safely.
For history geeks and curious readers in general, check out The Story of Rome, From the Earliest Times to the Death of Augustus, Told to Boys and Girls. I know, long title haha.
You don't have to sign up or register. You can download it for later reading, or read it online, through EPub, Kindle, etc. Have fun reading!