It is full of knife techniques and recipes. The cutting techniques, especially the ones with cucumbers, are nice to know.
About the three knife info - While there are hundreds of specialty Japanese knives, the vast majority of tasks are done with a yanagi-ba ( slicer) an usuba ( utility blade), and a deba ( break down knife). I might have added a santoku (three virtue - slice/dice/chop) blade. Basically, all other kitchen knives are versions of these blades. I make a set of three knives for customers of a yanagi-ba with 8" blade, a 5" or 6" usuba, and a thicker and heavier deba that looks like a heavy short chefs blade. A santoku is often added as a fourth knife.
I'll tell you the story about my most used kitchen knife.
It was a 10" vanadium steel wide blade slicer/chefs that my wife had, very thin … barely .060" at the spine .... and really sharp. Years ago, she tried to pry open a drawer that got stuck and broke 3" off the tip end. It sat in the block for years. It had belonged to her mother and she couldn't stand to throw it out. I took it out to the shop one day to re-grind it into a usable blade. I was thinking of making a santoku. I realized all it needed was to angle or curve the broken end down from the spine and it was a perfect usuba. Since the break was at a slight angle, I opted for angling the end in the Edo style. The job was done in minutes and since then I use it for 90% of all my cooking tasks. I have a block of other knives that are razor sharp, but this 1.5X5.5" blade laser is light and easy to use.
