I don't usually turn to self-help books precisely because I have a similar view about them as you do. Recently I even had a psychologist suggest me to read a self help book and "take what works". Though I understand that approach, I find it problematic because often the questionable parts might bring into question the validity or the soundness of the foundation upon which the "working parts" stand on. The whole book should be cohesive, it's not a bag of tricks with working parts among a lot of debris.