They’re mostly from his podcasts on Farnam Street and The Tim Ferriss Show. One or two are from his periscopes which are available on Youtube. Anything featuring Naval is extremely valuable, I would check out all the sources.
I don’t like them as a way to absorb books. If I’m not sold on a book, I would search google for a summary, then skim the summary to see if the ideas are interesting enough to pick up the book.