I've read it. He missed a couple of good ones, too. Barefoot also missed a few other printing errors, of less sinister things. (He catches a few pigs and what not, that are borderline, but misses bird's, which are rarely sinister, and quite a few cloud images mostly of objects that can look like teddy bears, pencils, knives, crosses. He also misses a lot of "dog's tails" sticking out of bushes. They become impossible to dismiss only when someone sees them and tells you what they are and what they are for. Also, I was only there for a few years, and couldn't vouch for everyone, and even suspected one artist of having mental problems while I was there. Still, I can tell from the book that he doesn't know how much of it was based on inexperience with art, printing, and photographic methods.
Derek might have also found it funny if he had looked at the typographic spacing "images" created by gaps between words and letters that form "rivers." When "rivers" got too bad we would just reset the spacing and sometimes even ask if we could throw in or remove an "indefinite article" here and there in the text. We've had times when if you squinted at a page you'd also see a diagonal cross or even a swastika. Not everyone is attuned to these images. Derek Barefoot is and quite a few pressmen would have welcomed his consultative services before these problems went out.