[sirbruce]

If you connect your Kindle via USB, you'll find the index files them in your system/Search Indexes folder. There's one for each book plus 2 other database files. But you can't tell the title. If you want to know if a book is indexed or not, just run a search from the home menu for a word and you'll get a list of books it appears in. You'll also get a listing of items not yet indexed.

In my experienced indexing takes anywhere from 15 seconds to 3 minutes per file; if you have a lot of books the time increases for the latter ones compared to the newer ones (probably because it has to search through a huge directory of all the previous indices). If you delete them they'll be regenerated the next time Kindle gets around to indexing that book.

I have had a few times where my Kindle 2 "forgets" it's indexing and claims none of the books are indexed. However, the files are still there on the Kindle, nothing is lost, and a quick reboot of the Kindle fixes the problem.