I get downright angry when I read something in a book that I am using in my own (incomplete!) book. Because then by the time my book is fit to be published it will look like I used someone else’s idea! I can’t stand it.
Although realistically most ideas have been used and reused already. They just come in different packaging and have different details. Still… it upsets me to think I could be criticized simply because someone else had their idea published before mine.