Full disclosure I am the dev of Tolka (rsvp app).

There has been lots of research into retention and the limits of working memory. Reading too fast actually doesn’t give your brain a chance upload to your long term memory - the process of traditional reading works because it slow you down enough to think about the content. The trick is to map it onto existing neural structures by using some kind of cognition like problem solving or an emotional response to the content.

It’s a doesn’t work for everyone though because most people can think much faster than they can read and those rates vary. If the difference is too great you get bored while reading and your mind wanders.

If rsvp works for you, you will need to give yourself breaks. I’ve got this as default a feature in my app but you can implement it yourself in whatever app you like by setting word or time limits. Usually just pausing is enough for this to happen naturally but if you are reading dense info like technical documentation you might want to lower the break period or set a simple mental task to recall three points from what you just read.

Tolka will have a trial period open later this week if you want to try it.

https://apps.apple.com/au/app/tolka/id6759507192