Depending on how similar the different books are, you could look into using conditional text (which can work with graphics and tables too).
Off the top of my head, you could use a few methods.
- Create a "master" book that contains all chapters (that need syncing). Be sure to turn off the numbering and pagination settings in the book. Use this book to sync everything you need.
- Update and sync one book. Open a chapter from one of the other books and manually sync the styles, parent pages, etc. Open up the other book file and sync the modified chapter to the other chapters. Repeat for the third book.
- Another option is to create a "master" style sheet document. Sync any changes into it; use the style sheet to update the other documents. I add this file to the end of the book and remove it when updating the TOC and exporting to PDF.