I only ever seem to make notes about a book in the two extremes - when something is put so beautifully I have to write it down, or - like now - when I hate it and can't resist snarky updates. Which I will probably be posting shortly in lieu of anything I ought to be doing.
And the bad ones I don't have to write down - they "stick". Sometimes I even remember the page numbers. It's the ones that are average or good but not great that are hardest for me to write.