If you are one of the Chapter members who purchased the Liability Insurance through the NFHS last fall you are still able to get both the 2020-2021 Rules Book and Case Book for free.
Each Book usually costs $6.99. I personally like having the Rules App on my phone because of the ability to easily search the entire content to find the information or specific reference that you are looking for. I have actually used this feature during the discussions at the chapter meetings.
Here is the link to the information. There are Apple, Android and ebook versions available.