on the time investment: "Ramit's Book-Buying Rule: If you're "thinking about" buying a book, just buy it. Don't waste 5 secs debating. Even 1 idea makes it worth it."
I disagree. Most non-fiction isn’t worth the book. That one idea can often be learned in a more interesting and faster way by watching a good talk by the author. By “not wasting five seconds” to consider if the book is worth it, you’re potentially wasting hours of your life (and some money) on a dud.