I started reading adult literature at about 14 or so and just read a lot. I find I retain more if I read faster where if I slow down I tend to drift off more.
Now this is just novels, technical information is a lot more dense and it can take me weeks to read a new programming language book cover to cover because I need to set it down after a while and think about it then go back and reread sections etc.
Speed reading is an entirely different thing, but I did spend a little while learning to read faster. The average person speaks about 180 words per minute at that pace a 120,000 word novel takes 11 hours. If you want to read a little faster don’t sub vocalize individual words just hear them in your head.
I will often set YouTube videos to 2x speed which is easily understandable and about the pace I tend to read. It’s bizarre but if you change the YouTube settings from 2x/1.5x to 1.0x it suddenly feels like most people are incredibly slow but those same videos feel fine when you start at 1.0x speed.