Short answer, I'm not the best example to answer these questions. So far the chapters are not things I've had trouble with. Long answer . . .
Usefulness? I'm not one to ever be short of ideas I'm not really sure of how I generate them. I tried to figure out if I learned anything on the first chapter and either my process (if I really have one) is different or exactly the same without thinking about it. The second chapter did point out to me that I need to set time limits for myself, other than that the grab sort and filter method is how I do things so I'll second it as useful advice.
Anything missed? I tried to figure this out on the first chapter but again, I fell flat trying to figure out why ideas pop in my head so I'm useless there. I don't see anything glaringly obvious on the second chapter but I'll follow through if I do think of anything.
Too long or short is subjective to the reader. If you read it and understand how to go about it, then there is enough information. If you don't need the information but need to trudge through it to understand what comes after, then it could be too long. So far it's comprehensible to me so it's not too short. I don't think I'd label it as too long because I can understand the need for the material.
As for being obvious, to me, so far it is but I don't think I'm the audience so far. I'll be most interested as this progresses.
What I've taken away so far. Something I've known about my research in different subjects is that I take too much time and need to worry less about missing something and more about getting things done.