InDesign Secrets had an article in 2014 on Indexing with InDesign you might find useful: http://indesignsecrets.com/alternatives-indesign-indexing.php
Live Index looks useful too if subsequently you're going to create a PDF or ePub: http://www.id-extras.com/products/liveindex
Many thanks for your posting - that was very helpful of you.
I'll look into the options you suggest.
Glad you found it helpful. I would add that indexing is a professional activity and if your book is important that you hire a professional indexer who's a member of an appropriate society, such as this UK one: http://www.indexers.org.uk
Fully agree with Derek - I adjusted one of these scripts for my own needs to work with entire books, but it still basically generates a plain concordance, which should only be used as a base for a professional index.
...Well, at least that's the theory. Can't count the number of occasions when I sent such a dumb concordance to a book editor, just to receive a short note "approved; please print".
At the other end of the spectrum: once, an editor complained that my concordance joined the page numbers for a certain pair of authors père et fils under one entry (how could a script know which one was mentioned?) and how page numbers were omitted on which something was clearly discussed (but not mentioned by name :/).
I have been evaluating IndexMatic2 and find that one big problem with it is that it doesn't appear able to import an Index Concordance from InDesign's own Topic List - which is a problem if you have already developed a list within InDesign.
I don't think it can import a concordance from anywhere, in fact, other than from a text file in its own proprietary format.