Make schemes, conceptual maps and so on, they will help you memorize stuff way easier than reading whole chapters off the book over and over, you can have an instant view of the subjects and they're also good when just repeating stuff before an exam.
Making written summaries also helps but it does require a bit extra time and effort so if you wanna keep studying "somehow" I'd say stick to simple and effective maps and schemes made up by key-words, you can read each chapter of the learning subject and underline the key-words then make a map linking all the main themes and words of that particular subject you're gonna study. You can make em on paper or even Power Point (which is easy as fuck).
Last but not least, again if you want to study "somehow", avoid trying to stay on books for hours and hours without ending up doing shit and getting distracted every 5 minutes, you'd rather have a good 1/2 hours of well done studying and then take like a 15/30 mins of pause to relax and later go back for another 1/2 or even more hours of study and so on.
Rinse and repeat daily, good luck with everything