Most self help books can be boiled down to very obvious tools and coping strategies. If it is the first time you have come across the concepts, it can be useful but if it isnt, it is useless.

Is paying 15$ too much to pay? If learning about an obvious but unknown idea for doing the things saves 10 minutes a week, it is.

Do you need to pay 15$ for the result? No. But a result is better than no result.