What exactly is your aerobic threshold? Definitively answer that question and you can publish a book, make money, and coach the rest of your life. I would say that aerobic threshold is usually slower than marathon pace. Perhaps it would be better to say that it is like four hour race pace. That may be your marathon pace but for competitive runners it is slower than marathon pace. It is supposed to be a little faster than easy. So that you breathe slightly harder but could continue at that pace a long time.
His second breakthrough was experimenting on out of shape old golfers. He had them run 15 minutes three times a week and all of their health improved. He called it jogging. In the past either you were a runner or you weren't. Now you didn't have to be a runner or a couch potato, you could be a jogger complete with 5k race t-shirts and sore muscles just like a real runner without the pressure to run every day and do well in races. As far as inventing sports go this had to be the greatest invention yet.
I have two of his books: Running With Lydiard and Running to the Top. The first is more of a general overview of how to run with the goal of racing faster. The second is more specific to being a really good runner not just running faster and it was 12 more pages and is three dollars less. I can't really recommend one over the other because honestly they are probably 85% exactly the same. Reading any of Lydiard's books is a perfect introduction to running and a read that no runner should skip. Many of his theories are still in use today by many of the top coaches. In fact the performance booms in Japan, Finland, Kenya, and other places can be traced back to Lydiard teaching coaches in those countries his basic principles.
Wether you run 15 minutes three times a week or 15 hours a week over 13 runs and play golf or run marathons you can stand to learn something from this coach of coaches.