Not every book that you receive will come from Amazon. For some individuals they do not purchase any books through Amazon. This does not mean that you cannot organize your books using Goodreads. It just means that you need to bring the books in Differently.
Scan in Your Book
If you have the Goodreads app installed in your phone or tablet then all you need to do to enter in a book is scan in the barcode. Scanning in the barcode is better then just searching for the title, since it will connect the book with the correct edition.
Search for Your book
Searching directly for a book will not be as accurate as importing books directly from Amazon, or using the barcode feature. However, there are many books were there are no other options then to search for them directly. If you have Audible books then searching is the only way, currently, to add them.
As you see below the novel Midnight at the Bright Ideas Bookstore by Matthrew J. Sullivan has 18 different editions even though it was only first published in June of 2017. There are older books that have hundreds of editions. If you just randomly click on What to Read Goodreads will mark you as reading the first entry.
If you really do not care if what you are reading matches up to the correct edition then you do not need to worry. However, since this is all about properly organizing your books it may be interesting to select the correct edition each time.