How do I merge a 2015.2 book version in CC indesign with a new version in 2015.3? Apparently my two devices were running different versions so they did not sync. Now I have different versions of the same book all with different stages of corrections. I would like to update or merge them into one if possible.
How were you trying to "sync" book? There's no "book sync" feature in InDesign. Book files as well as all InDesign files aren't supported for editing them on more than one computer.
InDesign CC 2015.2 and 2015.3 are stored in the same file format and that shouldn't make any difference.
You were probably copying different versions of the chapter files making up the book and editing on more than one computer. That's the problem.
You'll have to manually copy the files onto one computer and manually merge the latest versions of each chapter.
Unfortunate that one cannot edit on more than one computer. They made it seem as if CC is perfect for collaborating which included adding and deleting things, editing. Ugh!