Can you elaborate on the purchasing of executive summaries? Sounds interesting; I also like to forage and often find that, for certain books, I really just want the technical footnotes.
The other way of cheating is by watching talks by the authors, which give you the key concepts from the book in an hour. For example Simon Sinek presenting Why Leaders Eat Last (https://www.youtube.com/watch?v=ReRcHdeUG9Y)