All good ideas above so I will just add 3
Try study first thing in the morning doing so at night maybe affected by rebound from medication.
Ensure that do not have an associated learning disability ( mine is limited short term memory )that you need to work around.
My favourite is to have a pen or highlighter in hand writing as I read helped keep me focussed. With the advent of highlighters I used a yellow one to highlight important information. The second reading I used an orange one to highlight “lists” of points. And the third time a pink one give shape to the big picture. I would then review with a biro numbering informal lists or questions that have popped up. (Using my hands keeps me engaged with the work but does not do much for the resale value of the books)