Reading is useless
You can’t do decent revision through sitting with a boring textbook willing the information to go into your head. It will sit stubbornly, remaining in the textbook, refusing to make the jump into your bonce.
You have to do something with the information. Take notes, underline stuff, invest in a set of highlighters and colour code everything that moves, do drawings and put pieces of information into table form. If you do something with the information it will stay in your head way better than if you just sat there reading.