The best place to get Bill’s books is on the Bill Pottle Author Page at Amazon. Most of the books are in Kindle Unlimited. You can read Kindle books on any tablet or phone.
Most of the books are also available at Barnes and Noble, and some are also available in various bookstores. If they aren’t on the shelves, most stores can special order them.
You can also find most of the titles available as audiobooks on audible.com.