Recently my sister bought a collection of Mark Twain's books. She was wondering if they had enough value to be added to her insurance. It is a complete collection in excellent condition. Looks almost new. She bought this collection at auction for $100 and was wondering if they were worth more. Information follows: Author's National Edition. Published by Harper & Brothers Publishers. Printed on one of the pages : "This is the authorized uniform edition of all my books, Mark Twain." Copyright 1915 by Clara Gabrilowitch and Susan Lee Warner. Any ball park estimate would be helpful. She has no plans to sell them, she just wants to know their appraisal value, if any, for possible home owners insurance. Thank you, Al Baily