I love reading and I underline and make notes in books that I like.
A number of years ago I discovered that a squiggly line made freehanded, looked a lot neater than a straight line made freehanded. And when, a few years ago, CBD, accidentally included two of those Straight-Edged Rulers in my order, I fell in love with them.
The scalloped edge makes anything you underline look neat and important.
I usually buy 10 or 20 at a time and give them to friends or include them in gifts. I have a least 6 of them that I use all the time. I have one in with the pens and pencils anyplace I read,---kitchen, living room, family room, office, etc. I think they're great , and so do the people I give them to.