The term most used to describe tenkara is "simple."
Fellow tenkara angler Morgan Lyle has gone one better and has written a book on simple flies. There are some tenkara flies in the book, the iconic Ishigaki and the Takayama Sakasa Kebari, and some, like the CDC & Elk on the cover and the Stewart Black Spider (the first of the 52 patterns) that are not Japanese tenkara flies, but are certainly simple flies that work very well with tenkara rods. And of course, my favorite, the Killer Bug, is in there as well.
tenkara Radically Simple, Ultralight Fly Fishing - This is the first book on tenkara in English. I wish tenkara Radically Simple, Ultralight Fly Fishing had been written when I was starting out. Back then, very little information was available in English and the computerized translations of Japanese websites are really not very useful. Dr. Kevin Kelleher and Ms. Misako Ishimura (both tenkara anglers) have written a good introduction to tenkara for American anglers.
Reading Tenkara Fly Fishing Insights & Strategies is like sitting around a campfire and listening to a group of experienced tenkara anglers share some of their tips and tricks. You don't get to ask questions, but then again, you don't get smoke in your eyes, either.
The book is a compilation of interviews with tenkara anglers. The interviews are not presented one by one, start to finish, but broken up so that it reads more like a panel discussion on various tenkara topics. It's a nice way to lay out the material and makes the book a more interesting read.