I self studied this exam this past year and scored a 5. It is completely attainable as long as you are willing to put in a substantial amount of work towards preparation. Princeton Review prepared me more than Barrons. I bought the Friedland and Relyea textbook and didn’t use it very much as it went very in depth into individual case studies and I find it difficult to absorb information from reading. I’d recommend using Quizlet to memorize examples of legislation and case studies, both of which prove useful on the MC and open ended. Complete a couple of practice tests periodically to know where your weaknesses are as you approach the exam, so you can allot more time on what you struggle with. Keep your personal learning style in mind as you undergo this process. I learn by writing, so prior to the exam I wrote 3 sets of notes covering all of the material (one on lectures, one on PR, and one condensed copy typed up). Really, you’ll have to figure out what works best for you. I didn’t start serious preparation until the end of Janurary/start of February and did most of my studying late at night. Be sure to have some sort of schedule in place to ensure you keep on track throughout the year.
Many posts here on CC claim miraculous scores with a very short time spent prepping. In reality the surest way to ace the exam is through focused, lengthy preparation. Remember, the APES exam has one of the highest fail rates of all AP exams and less than 10% of students receive 5s. Don’t take that as discouraging, but approaching APES as a really easy AP is a mistake (Important for many who wish to study APES)
Best of luck to you on your journey with APES! It’s an interesting subject, and the self studying process itself carries much value!