Date of first copyright notice is 1973. First copyright term is 28 years, with option to renew for 67 years (total 95 years). I have no idea if the copyright was renewed - but it seems probable since the deadline was prior to John Naka's death.
Note that if revisions are made and new editions printed, the new material in the new editions can be covered under separate copyright, so even if the majority of a work falls into public domain, sections of the work may still be protected. Given the last copyright date of 1993, at least some material in the book is protected through 2021, and maybe longer - since I may not have the last / final edition of the book. Assuming the 1993 date is the final edition, the earliest the work in its entirety would fall into the public domain would be 2021, and if the estate (or owner of the copyright) decides to renew, at least parts of the book would remain under copyright through 2088. 95 years is a LONG time.
(by the way, notice how in the online scan of the book, the original scanner "conveniently" left out the copyright notices page)