This made me go back to review the blurbs I've written in recent years; if you click HERE (and scroll down), you'll see a selection of blurbs I've written. There, too, I am reminded of certain blurbs that I only was able to write because, first, I read a lot. For examples, the books by Anne Gorrick, Ric Carfagna, Christopher Stackhouse, and perhaps j/j hastain. I can recall, too, the struggle I experienced to write certain blurbs, e.g. on Nicholas Manning. I also see an early blurb that I don't think was used (probably because, even as a blurb, it wasn't that good).
Anyway, it's unexpectedly fruitful for me to look at the blurbs -- being able to see a (critical) mass of them makes me think there's a possible art form here that I've been missing. Must ponder this more ... and then undoubtedly engage.
And, yes, I haven't forgotten about this Blurbed Book Project. My attempts to write that book so far have only degenerated into false starts. Not to worry: I'm persistent!