re: The boards opinion on hunting dog training books?

Any of Richard Wolter's books are a great addition to a library. Retriever training is not rocket science, but Mr. Wolters was a rocket scientist.
I had the honor to do a seminar with him at an outdoor sportsman’s show. He was the lecturer and my dog and I did the demonstrations.
Getting to pick his brain for a couple of days was very insightful. He explained that his books were not the be all, end all to retriever training, but rather a primer based on utilizing animal behavioral science to accomplish some of the goals needed develop a working gun dog.
Many other good books exist on the subject, but his are good ones.
Steer clear of James lamb free for anything more than historical reference.