If you're able to demonstrate financial need to LSAC's satisfaction, you can get an LSAT fee waiver (in other words, you get to take the LSAT for free, and you get some other free law school admissions services from LSAC's Credential Assembly Service.
However, LSAC doesn't make it obvious to everyone that if you get an LSAT fee waiver, you're also entitled to a free copy of LSAT SuperPrep. All you have to do is ask.
If you got an LSAT fee waiver, email or call LSAC and ask for your free copy of LSAT SuperPrep.
However, make sure you get LSAT SuperPrep II (the newest edition of LSAT Superprep).
Details on this book in the May 2015 issue of the LSAC Report Newsletter (PDF p10):
New SuperPrep to Be Published
A new LSAT preparation book, The Official LSAT SuperPrep II, is being prepared for publication and should be available by mid-June. Like its predecessor—the original SuperPrep— published more than 10 years ago, the book will include three previously administered tests with an explanation for each question. This amounts to 303 mini-lessons. This practice book will help users learn how to approach LSAT questions as they prepare to take the test.
SuperPrep ll will replace SuperPrep as the test prep book provided to LSAC fee waiver recipients upon request (emphasis added).