The Best SAT Prep Book + Link SAT Practice Test Online

[Best SAT Prep Book] The most important book for SAT exam's preparation  is The Official SAT Study Guide (as known as the Blue Book) from the College Board. 
This is the only book which provides real test questions, and it’s important that you practice with complete tests featuring 10 official SAT® practice tests created by the test maker. With over 1,000 pages and more than 20 chapters, it's packed with the most up-to-date information regardless of the jacket and students need to get ready for the test.

FREE MATERIAL

In addition, some students need books that review the content tested and teach how that content is presented—including the secrets of the test. Personally I am a fan of PowerScore books---I know the author quite well ;). You can preview free chapters here: http://www.powerscore.com/sat/help/conte... 
But there are many SAT prep books written by test prep companies. You can buy books that cover all three subject areas (math, reading, and writing), or books that cover each section separately and in more depth. Look for books that explain the content tested (such as right triangles) and then show you how that content may appear on the SAT. Make sure they have a lot of practice questions after each content section so that you can master each topic.

You can also find some good free test prep online. Sparknotes has a decent SAT review, although they omit some important concepts and add a few that are not tested on the SAT. They do not delve into the tricks of the test, but they offer a great review of the content that is required.

Vocabulary, Math, and Writing Flashcards: http://www.powerscore.com/sat/help/conte...

Free Blue Book Database: http://www.powerscore.com/sat/help/conte...

Free Content Review: http://www.sparknotes.com/testprep/newsa...

OFFICIAL SAT PRACTICE TEST 2011-12
https://satonlinecourse.collegeboard.com...
Scoring Instructions: https://satonlinecourse.collegeboard.com...

OFFICIAL SAT PRACTICE TEST 2010-11
https://satonlinecourse.collegeboard.com...
Scoring Instructions: https://satonlinecourse.collegeboard.com...

OFFICIAL SAT PRACTICE TEST 2007-08
http://www.collegeboard.com/prod_downloa...

(Note: the Official Practice Tests from 2005, 2006, 2009, and 2013 are the same as the tests listed above).

To save money, visit your local library to see what they have in the way of test prep. They should have the Blue Book as well as some SAT prep books.

Good luck!