From my personal experience it's "letting reach exceed grasp." It's tedious and slow, but in the past, what worked was a pen, notebook and dictionary. I'd read until I reached a word/concept I didn't grasp then physically write it down along with the definition in my own words. Then I'd have to reread the paragraph until I looked at notes to grasp it. Then when the book was finished, I had forgotten half. I put the book away for a time to mull over notes and what I remembered, then went back and reread it later, referring to notes as needed. By the third or fourth reading, I pretty much had it. I did this with Shakespeare, Hawking and Dawkins.
I've been wanting to read more now but am putting it off because I've several vision problems that are degenerative. They can be corrected with surgery that costs a lot and I am currently uninsured. Add to that my current devices lack storage and reading online is a bit more challenging, even with corrective lenses. I can do it, but miss a good bit that I don't realize on first or second readings.
Oh wow. That means there's a non-zero chance they're lying about treating the extraordinarily renditioned well.
Edit: thank you for answering.