I've received enough emails from people asking the same question that I thought it would be good to post this again. Sing Like a Catholic is indeed available for free download. I'm very happy to have you read it online or send the link to anyone, or buy it with proceeds going to support scholarships for music students and seminarians seeking to learn chant.
It is much higher on the Amazon rank than I had ever expected, and I'm getting lots of great comments from people. Again, this book would not have been possible without this blog, which has taught me so much. In some ways, the readers of, and commentators on, this blog are all co-authors of this work.