Reading does not help with memorization. You need to close the book, take a pen and paper out, and write down everything that you remember. When you are done, check the book for what did you miss or get wrong. Think about why you forgot about it or got it wrong. Repeat the whole thing the next day.
This is a lot harder to do than just rereading the same thing again and again, the first time you try it it almost feels painful. But it is actually effective and will make you confident in your knowledge very quickly.