I haven't read the book, but from your description it doesn't look like especially useful advice to me. If it's obvious that a given investment has good fallba

I haven't read the book, but from your description it doesn't look like especially useful advice to me. If it's obvious that a given investment has good fallback value, then the market has probably factored that in already by the time you are investing. If it's not obvious, then the tip could be superseded by the more general one: "if you have information that most people don't and it makes you think that an investment will work, then go for it". But that is rather obvious, and the problem is to acquire that kind of information.