The short story is that this book is absolutely incredible, worth every penny, and increased my LR performance from getting 15 wrong every time to getting only four wrong every time. BUY IT, especially before you do any other kind of prep. Give yourself a month to get through it. It gives you concrete methods for how to attack every problem type.
The long story:
I had a roundabout way of getting to the point where I ordered this book. I took a Kaplan course and hated it. I did all of the homework and dedicated my life to the course for a month straight. It wasn't working. My score went from a 160 on the diagnostic to a 152, then a 154. The 160 diagnostic enabled me to enroll in their advanced course, but the course was completely unhelpful. Kaplan's methods aren't methods; they just say things like "oh, that is out of the scope, so it's wrong". Well, how do I know it's out of the scope? You don't. Or, you could probably figure it out, but that takes tons of time and on the LSAT you don't have tons of time. Kaplan does not give concrete reasons that can be applied to every question of the same type for determining why something is or isn't correct. The course wasn't working for me or improving my score, so after three weeks (the course was five weeks total), I dropped it. What a waste of over $1000.
I decided to get private tutoring. The tutoring company I used was brilliant for games, but also very expensive and I had already dropped a ton of money on the Kaplan course. I decided I'd look into using a book for LR instead. And I am saying this now to everyone who has not yet started prepping for the LSAT: BUY THIS BOOK BEFORE YOU TAKE A CLASS OR GET TUTORING OF ANY KIND. GIVE YOURSELF A MONTH WITH THIS BOOK BEFORE YOU DO ANY KIND OF LR PREP WHATSOEVER. This will save you a ton of money - the book is a HUGE bargain and worth every penny. It will also give you an excellent foundation for learning how to do every single kind of problem, and it is likely that you will not have to do any other kind of prep (ie tutoring or a class) once you read this book. You will obviously have to do a lot of practice problems and tests, but you won't need any other kind of instruction as to how to do the problems.
The main reason I like this book is it gives you an actual method as to how to do each problem type. My problem wasn't that I didn't understand why the right answer was right, it was that I couldn't finish in time, so I a) had to guess on the last five problems and b) sped up and my accuracy went out the window. By using the methods in this book, I was able to cut down on time for these problems so that I now always finish with at least three minutes to spare. The methods tell you how to look at a problem, what to look for, what is a likely incorrect answer (so that when you see it you can eliminate it very quickly without being tempted), and what a correct answer looks like. The most helpful piece of advice they give is that there is an identifiable and clear correct answer out of each of the choices. By using these methods, I was able to figure out what that answer was quickly, or at least figure out what the wrong answers were quickly.
The other thing to be said about this is that it is a long book. It's over 500 pages. GIVE YOURSELF ENOUGH TIME TO GET THROUGH IT. Skimming it, or just reading the methods, will not help you. You have to practice them until they become second nature. And you also have to give yourself enough time to actually get through all of the pages. I worked full time while getting through this, and I spent my lunch hour every day working through it, and was able to get through it in just over a month.
You can't expect this to work miracles overnight. But if you put in the time, it will help you increase your speed and accuracy without ever having to pay for a course or tutoring. Or, it will at least give you a sense of what kinds of problems you have trouble with, and then you can get the most out of tutoring by being efficient about it and targeting your weak areas. Or even if you don't get tutoring, you will know what kinds to practice.
I wasted $1000 before I picked this wonderful book up. Don't repeat my mistake. Use this as a first line of defense, and see just how far it will get you in your quest for a great LSAT score.
Note: I have not gotten my official LSAT score back yet. However, I did finish both LR sections with time to spare, and in practice exams, I had consistently gotten no more than four wrong on the LR sections in the past five tests i'd taken.