Today I passed CSA, and that was hard exam. Developer exam was really easy compared to this one. I am really glad that I decided to get official study guide after doing AWS practice exam. I basically went to developer exam after watching linuxacademy videos 3 times, doing labs twice, read the whitepapers and got 90% from both (aws) practice exam and actual exam. Did same with CSA practice exam and got 80 % (+96% on linuxacademy final exam). At that point, i decided to get the official study guide and read that, rewatched videos and white papers and still got only 70%. Good thing I got the book, seems like they removed all easy questions and I guess they adjusted passing score (or at least someone is claiming that he passed with 58% on reddit). I really think the book is mandatory, or you have to read AWS documentation pages thoroughly. When you are in the exam, don't be alarmed if you don't know the answer to every question, just flag the most difficult ones and get easy ones first and then go through the hard ones. I did spend a bit too much time on harder ones at the beginning.
edit: just want to clarify that Linuxacademy really helped me to get a general idea whats what. I just want to give heads up for everyone else and wanna share my guess that after the introduction of "optional" certification level associate exams are bit harder and other similar training sites to linuxacademy are having same problem of having final exams bit too easy, at least until they have time to react. I doubt developer examI took 2 months ago was suppose to be that much easier.