Maybe you're being too hard on yourself? I mean your expectations may be too high? It has good reviews there, and seems pretty creditable. I liked the first chapter, which I've just read. I think I'd be happy with it. Lots of famous authors have written many more books than the books they are known for. And those are the famous ones! The attrition rate is high. In your situation, I would seek to find out what 'normal' is and then I'd measure myself against that.