First, If you are looking for this Certification, make sure you truly are a practitioner. Im one of the ones who started Agile at my company (Big company) and I can tell you that you need to know about the market, Portfolio Management and Strategies to make the Transformation.
Cornelius Fitcher its something like Rita book, they are both pretty good, and I do recommend starting with Rita, then with Cornelius there is many things that you will understand!, because Agile is simple, but as we use to think like Certified PMPs, is difficult to understand. Specific Lessons from Cornelius are very useful.
I obtained a very good grade, of course passed everything, the exam was so easy form me!, I was expecting much more!.... I was laughing and ended plenty of time. Make sure you study for you!, to personally grow up!, and you are a true practitioner.
Love you all!, Best Regards,
Erick Leiva Lopez