ENISA Cloud Computing Security Risk Assessment
The European Network and Information Security Agency wrote "Cloud Computing Benefits, risks and recommendations for information security."
This document, the "ENISA cloud document" for short, is a document with a lot of interesting method and material in it. Some of it is more usable than the CSA guidance. Some of it can be skimmed, in particular the 'boring tables'. Yet, you will need to read this if you want to pass the exam.
However, it is not necessary to read it now to follow the course, so you can just download it, and read it later.
Note that there is a specific "Study guide ENISA" later, with more explicit instructions on what to read and what to skip.