Ah. I do have similar issue, that usually, at once, I will struggle to read for over a hour. Thankfully, found a way, that works. 10-40 minutes reading -> 5 minute break -> 10-40 minutes reading of different book -> and so, loop this. And if I do this often enough, there will be times, where I actually do manage to somehow pull off more than an hour, without said break.

Anyhow, take your time :D, and make small steps. I myself, went from reading ~10h a month at the start of the year, to then 30h, and… the amounts that I am pulling off now. I believ in you