There are three types of Study Aids. The first will be discussed here.
There are books that give you a summarized version of the cases that are probably in your textbook in a particular class. Some of these study aids are customized to the most popular textbooks, so they present the cases in order. You can see some examples from Amazon.com, which normally has the best prices:
Often these are “keyed” to a casebook, which means the order of cases and topics in the study aid will be the same as your particular casebook. If a study aid is keyed to a casebook, it normally will say “Keyed to (author name)” on the cover. A keyed study aid is nice because it saves a little time finding a case, but it is not always available, nor is it necessary.