I just bought it as a Christmas present for myself from Kobo. As an e-book it cost me under NZ$10 - a real bargain!
Roger Taylor has produced a fifth book, Mingming II & The Impossible Voyage
Details on YouTube https://youtu.be/WIinkyKwjdw
and on Roger’s website http://www.thesimplesailor.com/
Kind regards,
Pete Shepherd