One other thing we've added for revision tracking are Revisions. :) These can be found in the Format menu, and basically all they do is colour your text according to the revision level. Red, blue, green, etc. The trick is they force that colour to be used for everything you do (except deletions, Snapshots will remain the best tool for that). You can then at a glance see all of the small things you've changed, and when you are done with a revision, you can easily wipe them all out in that same menu. Additionally, the Find by Formatting feature in the Edit/Find menu has a revision search tool within it. You can search by revision "pen" in a step-by-step way, jumping through your entire book.

This feature is also great if you are working with a co-author.