Wants to Create IPad App Based on Book

Dear Rich: I want to create an iPad App based on a book published in 1999. I contacted the Authors and they told me that the publisher owns the rights. I contacted the publisher and they said: "If you would like to make an app that uses elements of the book and is quite interactive -- those rights are controlled by the authors." Are "interactive" rights often separated from "book" rights?  Yes, publishing agreements can separate interactive rights from traditional print rights. Whether an author retains interactive rights has to do with the publisher, the time when the agreement was negotiated (currently, the trend is for publishers to retain all rights), and the author's bargaining power.
Rights associated with a book are always separable. Typically, the publisher obtains worldwide English-language print rights. These are the rights to sell book versions of the work and nowadays that includes "passive" eBook versions -- for example, Kindle, ePub or Mobi book rights. These eBook formats are passive, not interactive, or as publishing attorney Lloyd Jassin states, these are "verbatim" displays of text. (Note, older "legacy" contracts were not clear about who retained these ebook rights.) Enhanced eBooks, such as are often sold in iBook or App format often include features that allow the reader to engage additional content or media or otherwise engage the user. They are considered interactive, and Jassin believes that most publishers are not in a position to exploit them. In the old days --  back in the 1990s, interactive rights might only be applicable for videogames or CD-Rom applications based on the book. But nowadays the borders are often blurred. The closer the work is to a verbatim reproduction of the text, the less likely it would be considered interactive ... Wow, have eBooks really been around for 40 years? ...