One book that's not half bad is "Fear". Also, I liked some of his pulps- not just the Sci Fi ones- he wrote Westerns. Had several pen names. But then again, I actually like pulps in general. Some were well written.
Dianetics was the self help thing. It was really grass roots when it came about though of course even then Hubbard was trying to expand it. It had no religious aspects. Scientology came about in 1953 and there you get the spirituality aspects.
As I said, I'd not mentioned anything about Hubbard being a good guy or well intentioned. I was only discussing his competence.
I also said I could and would possibly later discuss the efficacy of Dn and Scn. So I'll bring that up now. I have personally seen people get a lot out of Dianetics and Scientology auditing. I've gotten a lot out of it. My pcs have as well. The TRs really do help with the basics of communication. Another thing Hubbard did was tie his theories together to get some continuity. So the ethics stuff dovetails with auditing which dovetails with the TRs as well. The data series also interfaces similarly as does other "admin tech". Do I think everything about it is perfect and flawless? No. Absolutely not. But, yes, it is effective. That's why there are so many exes and other critics who are genuinely afraid of it and say it's dangerous. If it did not produce effects, it could not engender any dangerous situations- it couldn't be used that way, it couldn't have any such side effects.