this really depend on when you feel more comfortable or more confident.
every people have different level, so they need diff time to prepare. for me, i finished the kaplan book in June(used 2 weeks), but at that time i still need to improve my verbal (I'm an international student), so i spend the rest on verbal (1h per day) till around 1 week before Oct exam. i redo the kaplan book one more time in the one week to get fresh memory
kaplan is the only book i used and i'm 99% confident with the stuff inside, i get 95% total in exam.
i highly recommend you do the pratice test ahead of time,so you know what is covered in the test. kaplan book does not cover some area in the test (i only did the practice one night before, so i missed some questions on the test just because i did not know the coverage)
hope it helps, good luck🙂