PQRST study method

Skim the headings of the entire chapter. Your most important goal is to find out how the chapter is organized.
If the major terms in the headings are unfamiliar - look them up
The same material could be organized more than one way. If the way it is organized helps you to remember the main topics, then use that organization. If you notice some other way it could have been organized that makes more sense to you, then use that method.

Turn the subheadings under the major headings into questions that you expect to be answered in that part of the text.

Try to see if the questions you anticipated are answered. Reflect on what you read; put it in your own words. Try to connect what you are reading to things you already know. Don't mark or highlight words or passages as you come to them the first time. Wait until you have reached the end of a small section, maybe a paragraph or two and look back to decide if there is anything there that you probably wouldn't remember without highlighting it. Try to learn through trial and error how much marking is the minimum you need to do to remember all the material.

This is the most critical part.
After reading a small section, perhaps a page or two CLOSE THE BOOK and try to write down the main ideas and as many details as you can, and then check yourself.
Put the main ideas and details in your own words; don't just memorize the exact words in the text.
When you check, look for important things you omitted or got wrong.
Do it again. Do it as many times as you need to until you can close the book and reproduce the material accurately, but meaningfully, not just by rote.
Once you can do that immediately after closing the book, then start trying to do it after being away from the book for a while. First short gaps, like an hour, then longer gaps, like a day or two.
This is hard work. You might start by first trying to be able to make just a skeletal outline and build up the ability to fill in details.
Develop your own mnemonics for memorizing major points, or any details that you find confusing.

After some time has passed, try to reproduce the material as you did above. The key here is that you must give yourself enough time to forget some of the material so that you are forced to really re-generate the material. Re-generate means that you use your mnemonics and connections from the easier-to-remember main ideas to pull up the details.
Research has shown that reflection, spacing your study, and organizing all improve learning significantly.