This. Every single technical book I own is full of markers, annotations and references between pages in the same book and to other books, as well as notes writ

This. Every single technical book I own is full of markers, annotations and references between pages in the same book and to other books, as well as notes written down and jammed between the pages. btw. this is why it really annoys me when publishers print textbooks with insufficient whitespace around the text columns. Where the hell am I supposed to write then? :D