The best way to keep books clean is to read them. When you take a book off your book shelf, the dust is dislodged.If you have books as a collection instead of reading them, you need to do the dusting at least once a month.
Its better to use a lambswool duster instead of a feather one as the hard spines of feather dusters may catch on books and tear them.
You need to do a thorough clean once a year by taking all the books off the book shelf.

• Clean the book shelf thoroughly by using the crevice tools to get into all the corners
• Dust the top of each book with the upholstery attachment on a vacuum cleaner on a low setting
• Hold the book upright, whisk the brush quickly along the top, from the spine outwards

• Wrap the book in acid free tissue pager
• Put it in a polythene bag
• Put them in freezer for seven days
• Take the book out the freezer, and allow it to return to room temperature slowly
• Brush mildew off in the same way as talked above