LSAT prep

Hey guys I'm in my 12th grade rn. I'm studying in India and I'm going to a uni to do my 5 year LLB hons degree. I've always wanted to get into an ivy for law so I really wanna start preparing for my LSAT. I'm looking for good books to start with. Could somebody please help me out with this and I'm also looking for advice about whether I should start early or wait.