It is my best opinion that this book is a part of the Public Domain. United States copyright law is rather complicated, but from using the many resources available at the Stanford Copyright and Fair Use Center, I am confident that this opinion is correct. That includes the Digital Copyright Slider, searching Stanford’s Copyright Renewal Database as well as the Library of Congress’s Copyright Catalog.
Canadian (and other international copyrights) I am less confident of.
Original Copyright Statement:
Copyright © 1961 by Sandor Voros. First Edition. All Rights Reserved. Published in Philadelphia by Chilton Company, and simultaneously in Toronto, Canada, by Ambassador Books, Ltd. Library of Congress Catalog Card Number 61-9024. Designed by William E. Lickfield. Manufactured in the United States of America by Quinn & Boden Company, Inc. Rahway, N.J.
I was considering republishing this book, so if it is in the public domain as you say, that would be one less hurdle. If it is published in the US or simultaneously, then I think the US law “trumps” other law; at least here. In most cases, the rights revert back after a set amount of time, and since Chilton may not even be in business, you are in pretty good shape.