Copyright law strikes once again

One of the ideas that I've been thinking about of late is the conversion of some older works into audiobook format. One such book that I was examining is Machen's Christianity and Liberalism, published in 1923. This book appears to be in the public domain in Canada, where copyright terms are listed on Wikipedia as life of author plus 50 years. As such it seems that I could do whatever I want with that text in Canada.

The situation is not quite the same as far as the US is concerned, where 1923 is a special date in copyright law. Works published in 1923 or later have longer copyright terms (although in some cases copyright renewal was required). This means that this same book appears not to be in the public domain in the US. And this would be a problem, as my website is hosted in the US and I suspect that many of those who might be interested in this material in audiobook form might would also be located there. Probably enough of a showstopper to cause me to look elsewhere for something to convert...