I’m reading in Preview on the latest macOS, 10.14.4. Should I be able to click links in the PDF version this way?
I just re-downloaded the PDF to make sure. While the YouTube link on page 13 works, the links on page 54 are styled as links, pretty obviously intended to be links, but the link-styled text is not actually a link, does not navigate to the intended website when clicked, and is not actually clickable. There are some more of these on page 55 that also exhibit the problem, indicating it may be a book-wide problem. The YouTube link that works is explicit link text, with “http://youtube.com…”, while the broken links are like an anchor with a body but no href.
No big deal for me—I imagine most of these are easily found by searching—but I’d imagine you might want to fix this.