This is one of the first books that will be dropped. I had 7 books drop in a single battle within the first 5 hours of gameplay. You will find books in red chests dropped by "named enemy officers" or by taking over bases. All chest except for the book of explosives and engineering ARE time sensitive. So there is nothing you can do to expedite the process. You may find one book during a battle or you may find 4 or more.