How do the ibooks apps (viewer AND author) identify a publication?

I have a recurring frustration with my own iBooks that I have created in iBooks Author.

I should start by saying that in some cases I created an original publication and layout (Call that BOOK 1) and then later duplicated that file to create a similar publication with different content (Call this BOOK 2). With the second ibooks author file, I used a different file name, a different TITLE (in all applicable areas - the Cover Title, the relevant areas of the inspector (along with the author name), etc.

In the end I have two very different publications of vastly different file sizes, content, titles, etc.

Whichever iBook I first load into the iBooks (reader) app (say, BOOK 1) loads perfectly. Then when I try to do the same with the "relative," it accuses BOOK 2 of being a duplicate of the one already in my library. The only way to read BOOK 2 is to delete BOOK 1 and then load BOOK 2 into my library (at which point it accurately). If I want to read BOOK 1... yep... I have to first delete BOOK 2.

This trend has now expanded... as I have made 5 or 6 publications from the same beginning template, and this has made for a frustrating experience with the concept of having a "library" containing the full collection.

What am I missing? I see that the files copied into my User Accounts library are strings of numbers, not names. Is this number somehow created upon the creation of a new (fresh) ibook project in iBooks Author, and thus never changes regardless of how many times I make edits to the title (or file name) of the book?

Arrrrrggghhh. Any help GREATLY appreciated!