I think writing on the margins of the book and underlining (even vertical underlining, which is very quick) is a good compromise. I rarely read without a penci

I think writing on the margins of the book and underlining (even vertical underlining, which is very quick) is a good compromise. I rarely read without a pencil these days. It is low effort and helps me find interesting bits later and engage with the book. I am probably not really brilliant, so YMMV :)