Do not buy CMMRS. If someone offers CMMRS to you for free, say no. If someone will PAY you to take their copy of CMMRS, pocket the cash and throw the book in the trashbin.
I swear, CMMRS is far and away the worst book I have encountered in medical school. The book is horribly organized and was basically written by someone with the same sense of humor as a pre-pubescent 5th grader. The jokes are not funny, the mnemonics are not memorable, and the charts are only helpful as a quick reference - not as a way to learn. Half of the written material is pretty much trying to explain the reasons you should memorize their crappy drawing or mnemonic without actually explaining the science behind it.
I give the book 0 stars. Seriously, I was never in support of book-burning until I read this piece of garbage.
... Try some form of microbiology cards instead, and use your course and lecture materials to generate your own study aids. I'm serious.