Volume IV is the first volume of the Black Medicine series that I picked up. Other reviewers point out that this book is not meant to stand alone but be read in conjunction with the other books, especially the 1st and 2nd in the series. After reading the book, I can understand this perspective. Volume IV explains how to use a variety of weapons. The focus is on how to actually use the weapon--how to hold it, how to take off the safety, etc. There is less discussion of points of attack, but this is the topic that is covered in previous volumes.
How effective is the book? If you could internalize all the information in these books, it would probably give you an advantage in certain situations. What those situations are, I'm not sure. I have seen news reports of people being attacked with swords (actually, I remember a case in England where attackers were fought off by a bystander with a samurai sword who disappeared after saving the victim, never to be seen again), but what is the likelihood?
Part of the interest of this series is the authors' humor. Example: "...you pull the trigger. Nothing happens. Now what do you do? If you throw the gun at him, I will track you down and kill you myself..."
If you are on a short budget, you are probably better served spending your money on something else, like a home-security system. If not, you might enjoy this book and find it useful.