If you noticed errors, poor printing, or some problem with the mechanical preparation of the book, you could mention those, too. Your overall assessment of the book. Do not waste people's time getting them to introduce you to a subject when you could be getting more detailed information or their unique viewpoints. Explain who you are and the purpose of the interview. Be prepared to take accurate notes.
Tape recorders make some people squeamish.
This means that you will not reveal their names and will, if necessary, disguise their identities in your writing. If you make this promise, keep it. After you ask questions, give people a chance to add any comments they consider important. These final words are sometimes the most interesting. Offer to send them a completed copy of your paper or report.