It seems like if you need to remind yourself if you’ve read today or not you aren’t doing “deep reading”.

Schopenhauer’s essay “On Reading” is instructive here. He recommends reading fewer books but going deeper into them.

While listening to Derek Sivers and Shane Parish talk about reading, I found Derek's comment to be, what I think, is a way to 'go deeper': assuming you've made highlights in a book, when you finish it, spend time thinking about each highlight. Take unnecessary words out of the highlighted text. Get to the core of the words that really triggered you to think different. I've yet to do this.