No matter what book you buy, get the official SAT studyguide (blue book) to supplement it with. That way, you can do “studying” in another book and take real practice tests in the blue book. It worked best for me- I had the Princeton Review book, by the way. It did the job.
@ILikePlants self-study is honestly the best way to go. Kaplan classes teach study skills basically. Just have the diligence and patience to keep yourself motivated and you’ll be fine.