I often read books too quickly. When I read fiction (particularly exciting fiction), a paceless “reading in my head” means I find myself skipping over whole lines at a time as I scan for the next piece of action. I don't think this is very good. I miss out on important plot details, and also on actually reading a not-insignificant part of the book. The paper-skimming which may have aggravated this issue, of course, relies on the fact that you do not want to read a not-insignificant part of the paper.
Recently, prompted by one of those “me and pookie” Instagram reels, which survive by being forwarded around in DMs between young lovers like memetic STDs, I tried reading part of my current book out loud, to my girlfriend, just as we went to bed. I would highly recommend this: it's much better than reading a book to yourself by the light of a smartphone, it's intimate and cozy, and it forces you to read every word, at an even pace. I was surprised to find myself reading much more carefully and slowly for several days after doing this, even when alone. It's a good habit to read every word, when care has been taken to write every word, particularly in an era where the proportion of what I read where this is not true seems to be growing rapidly. It's also a good way to notice and later remember Chekhov's Guns.
So, in summary, I highly recommend reading a book out loud, to anyone who will let you do it.