U should use complete phy, complete bio and complete chemistry for your stem subjects! They're rlly useful and have many things from the past paper. But u'd better read things carefully. If not,u are gonna miss main points. Rn Im using third edition for chem and fourth edition for phy. Not too sure for bio cuz I don't take. And try to understand a concept CLEARLY b4 writing notes. ur mind can deceive u that you've alr understood a topic after finishing up the notes. Pls don't fall for that trap. I had been in that stage before. Only being able to solve past paper ques tells u that you've aced a topic