This book is exactly what you need to understand the factors that determine rarity and value. It contains a comprehensive delineation of the varieties of each sword part, maker dates and places, and a good dose of relevant history to the development and use of the sword.
This is not the ONLY book you need - but it should be the first.
This small investment can literally save you thousands in mistaken purchases...you will quickly see why you should save your money, i.e. don't buy several $400 swords from Ebay, and rather purchase the "special" (albeit expensive) blade.
There are too many hoaxers out there, and you need to visualize your purpose. Do you want a fragile 15th century relic? A modern (and very pricey) blade of Iaido practice? A WWII (and prior) collectible? What's the difference?
Why be able to read the maker's mark? What difference doe it make? Do you want the master's blade, the student's blade or the machine made? Better find out the difference before you invest.
Would you buy coins without a Redbook? Stamps without a Scotts'?
This is a fairly serious overview of Samurai swords intended for someone who is interested in collecting them (or perhaps has inherited one). That is, this is quite a 'theoretical' book intended to convey, in a quite concise manner, the myriad of details needed to identify Samurai swords.
The book goes through a very brief overview of Japan's sword history including some very rough information on the swords produced in various time periods. Mixed in here is a tiny amount of non-technical information in the form of some tales of how the special clay-coating heat-treating process was invented.
The book then presents detailed information on such subjects as blade curvature, temper lines, tip profile, tang markings and finishing. This section has a number of line drawings that do help convey the information in a clear and simple manner.
This leads into a very in-depth section with the Japanese characters that could be found on a sword tang. This section is quite long and, considering the book's purpose, not really very useful to the majority of people. That is, without understanding Japanese you really aren't likely to be able to use this section - it would be much better to consult with someone who does understand Japanese.
I really had hoped for more of an overview of the history with some details on the more famous crafters. There is also very little information on the manufacturing process other than some very cursory paragraphs and drawings. I agree that this subject deserves many books but I also think that since it is not really highlighted in this volume, a beginner will have no real reason to understand WHY certain eras and smiths were regarded so highly. That is, without more background on the process one is left asking the question "what is wrong with a stainless-steel blade?".
One for the serious collector but you will definitely need other books on the subject to really get an appreciation of the remarkable nature of the Samurai sword.