I'm going to be re-issuing one of my non-fiction titles, to add additional material. There's no question that it will be a new edition, so that means a new ISBN. However, I had to cut some explanatory information from the first edition to keep it under Amazon's page count limit. With the new material, I'll definitely be over. That means I'm looking at two volumes -- which will also allow me to restore the content I had to eliminate from the first edition. Am I correct that each volume of the new edition has to have its own ISBN?
Update: According to R.R. Bowker a 2-volume edition only requires one ISBN. However, Amazon KDP can't handle that, so to self publish it through KDP will require two ISBNs. No response from Barnes & Noble as to whether or not they'll take it as a 2-volume set.
A two volume edition on Amazon would only require one isbn if it was a two volume set sold as a single item… but there are no print on demand services that can cope with that… you could use a printer but all things considered it’s probably easier to sell it as parts 1 and 2 separately via pod and use two isbns another option would be a thorough edit by a new editor to get it under the word limit because that’s some long book
Unfortunately, an edit to reduce word count is not possible. The book(s) is/are primarily a collection of lengthy, historical documents with my contribution as editor being a brief introduction (1 to 3 pages each) to each document. Many of the source documents run into the hundreds of pages. So it appears that I'm going to be issuing two books, and trying to link them somehow in the descriptions on Amazon.
Yes. That's apparently what I'll have to do, but they aren't really a series, any more than the multiple volumes of the Encyclopedia Britannica are a "series." But, as the saying goes, ya gotta play the hand you're dealt.