Just to close this thread, I contacted George Breckenridge via his utterPower website, and asked him about the book - he replied very quickly and in exchange for contribution towards website running costs, sent me a link to download a PDF of the book. It's excellent, exactly what I was looking for, well written and loads of technical information. So, thanks for the pointers, everyone.
And to Hugh, it's threeReefs as in heavy-weather sailing, which I used to do when I was somewhat fitter.
Richard