What else would you call all that chemical energy used up when neurons are firing etc to allow you to read and remember something if not mental effort?

All things we do requires mental effort. Laying in bed and daydreaming also results in neurons firing. So, I think we're just discussing the amount of effort. My point was that self-help is usually written is such a way to make its reading very pleasant and to actually be a dopamine hit - it makes the reader imagine all the potential changes they can implement in their lives, it pumps them up with positive message etc. It feels good to read it. However, in vast majority of cases, people remember and try to apply the advice for a couple weeks at most, and after that life happens, habits take over and they're back to their default.