Supplements, much like beauty, are in the eye of the beholder. Just as one may debate the beauty of a wrinkly-faced bulldog, many will debate the usefulness of study supplements. Even amongst those who favored the books, there is disagreement over which ones are the most handy.
Some prefer long outlines. Others prefer weighty tomes of treatises intended for practitioners (we call those people gunners). And of course, others think that supplements are for suckers who'd rather waste $20 on a book than study the materials provided for class. Here are a few assorted opinions, courtesy of the FindLaw bloggers:
My favorite supplement, by far, was Professor Glannon's Civil Procedure: Examples and Explanations. It gave the black letter law summaries, followed by Q&As to test your retention, and even made the much-maligned Erie Doctrine somewhat comprehensible. Other great E&Es were Federal Income Tax of Individuals and Administrative Law.
The supplements I hated most were the "In a Nutshell" series. They are tiny little books that despite their diminutive height, were about 500 pages thick and chock full of small print. I'd venture a guess that they'd be great for studying while, say, hiking, but for those traipsing between their apartments and the library, you can handle the heft (and large print) of full-sized books.
One more note, that should be obvious. When choosing supplements, if your professor has written one, like my Civil Procedure II professor did, pick that one. And if you pick up books of prepared case briefs, make sure you match the casebook's author and edition, though nowadays, most case briefs can be found online for free.
Whatever you do, don't buy a law dictionary. (Sorry Gabriella!) You can find them online for free (at FindLaw.com, perhaps), or if your school provides access to either of the two big legal research databases, each has its own law dictionary.
These were my top five study aids in law school:
I was generally anti-supplement, but I did make use of many, many online resources.
(Editor's Note: The opinions voiced here are just that, opinions. No consideration was sought or given, and no breaks where handed out. Not even to aides published by our mothership, West. We just called it like we saw it.)