I've put all my chapters in a book and created an Index. All is well until I try to edit the Index. InDesigns materials tell me to go to my Index Preview Panel to make edits, which works fine. But the Panel does not contain all my index entries. I've tried updating the previews and regenerating the Index numerous times, but I still cannot get an up-to-date preview panel. Any ideas???
Well, I may be five years too late, but I have just discovered that the preview panel does not populate unless all files in the book (those files represented in the index, at least) are open on the desktop. That is: the index entries of only those files that are open are represented in the preview window. Index entries of closed files are not represented in the preview.
Sorry you had to wait five years to find out. Glad I could help.