The Steck-Vaughn complete GED preparation is a complete 5 topic study guide for passing the GED.
You start out using this book by taking a self timed practice test for each subject. (You can do all 5 at once, or 1 at a time.)
You then "grade" your practice test with the answer sheet provided at the back of the book.
When you are done "grading" your practice test there is an analysis sheet for each subject that shows you what lessons you need to study based on your correct/incorrect answers.
At the end of each lesson, there are practice tests based on the specific lesson learned.
After you have reviewed all lessons in all 5 subjects you need to, there is a final GED practice test in the back of the book.
One of the great things about this book is they give explanations for all the correct answers and why one answer is more correct than another.
Steck-Vaughn also has Exercise books that go along with this book:
Ged Mathematics: Exercise Book (Steck-Vaughn GED)
Social Studies Exercise Book (Steck-Vaughn GED)
Ged Language Arts, Reading Exercise Book
Ged Science Exercise Workbook (Steck-Vaughn GED)
If you don't have "basic" reading and writing skills, you will struggle trying to use this book. I think anyone with a 6th grade reading level should be fine.
As for the GED itself:
If you can read, write & comprehend - you will pass.
Social Studies and Science are just reading comprehension. All the information you need to answer all of the questions in these subjects are in the tests. You are given paragraphs to read, you then extract the information to the questions they are asking from the paragraphs you read.
Language Arts: Reading & Writing is about sentence structure, punctuation, mechanics & organization. As long as you use complete sentences and have clear ideas on your writing essay, you will pass. (Spelling does not matter as much as you would think on the writing portion of the test.)
Mathematics is the hardest subject for me, I fear math because I never learned it but fret not. You are given a "cheat sheet" when you take the math portion of the GED, this "cheat sheet" consists of mathematical formulas -- that's right -- you don't need to memorize the mathematical formulas, you just need to know how to use the formula to solve the problem. As I stated before, if you can read and comprehend you won't have a problem using this book to learn how to solve the problems using a specific formula. Oh did I mention you can use a calculator on the first part of the math test? Yes, sorry I forgot to mention that there are two parts to the math test. The first part of the GED math test is multiple choice and you can use a calculator, multiple choice questions make up 80% of the test, while 20% are open questions.
P.S. The GED is going to go through a complete overhaul beginning in 2014. Rumor has it there are going to be two GED tests. The first GED test for those who want a GED for employment purposes which will be similar to the current GED. The second GED test is for those who want continuing education, this test will be different as it will be more comprehensive and incorporate community college admission placement tests to better the education of GED entrance to the college level.