Goodreads Librarians Group discussion

I have an edition of this book which is not listed, but when I search the ISBN, only the original edition comes up. The ISBN is 0770000118. The book that I have is the 3rd printing and it has a different cover, but it won't let me add it because it's the same ISBN. How can I go about adding this book?

Here is the information:

Anne of the Island (Anne of Green Gables #3) by L.M. Montgomery.
First Canadian Paperback Edition, 1968. Published by McGraw-Hill Ryerson Ltd. 326 pages.

Description:
"In the third in the immensely popular series of ANNE books, the once little girl of Green Gables is entering her eighteenth year. Life is full of surprise, adventure and new impressions as Anne enrols at college. She must face unfamiliar surroundings and strange faces, but before long she is building new friendships and finding romance."

The cover is: http://pictures.abebooks.com/isbn/978...

Create an alternate cover edition, see http://www.goodreads.com/help/show/85...