Trying to understand ISBN/ASIN use/re-use

[Jeff]

I came across a different edition of this book than what I had originally shelved. I had originally added this hardcover edition of the single book: https://www.goodreads.com/book/show/7...
But instead, this edition (Readers Digest editions of The Partner and 3 other books) was showing in my shelves: https://www.goodreads.com/book/show/9...

I'm just trying to understand the policies regarding these changes. Both editions have the same ISBNs (10 and 13) in Amazon, and the ASIN for the Readers Digest edition is also in Amazon. The original hardcover edition has a librarian note that the ISBNs were re-used by the Readers Digest Edition. It also has ISBNs that I can't find either in Amazon or Worldcat, but does bring up some links to this book when I google it.