Regardless of how overpriced some of these materials are I would encourage anybody who is serious about getting an awesome GMAT score to work through all of this stuff. For GMAT tutoring you will need all of these materials.
GMAT Official Guide 2017: This is the single best resource of Official GMAT practice questions and a must buy for anyone remotely serious about preparing for the GMAT. Don't look here for GMAT strategies or teaching material. It is really only for practice. To save a bit of cash, grab the OG 2017 bundle with the main guide, the quant review, and the verbal review.
The Official Guide for Quantitative Review 2017: Similar to the main guide but focused on Quant. The difficulty level is a bit lower than the that of the main guide but this is still a great book for building up your quant skills on Official GMAT questions. Not a must buy but good enough that I use it with just about every GMAT tutoring student.
The Official Guide for Verbal Review 2017: Same idea as the quantitative review. An excellent additional bank of official GMAT verbal questions. Another optional one but I'd strongly recommend going for it. Again, I use it in GMAT tutoring.
Exam Pack 1: Two more official GMAT practice tests! These are a must have. Stellar practice for the end of your preparation. Here are some recommendations on how to use your GMAT practice tests and a review of the Exam Pack. Also - use a simulated GMAT pad for all practice tests. Better to practice as you will take the test.
Exam Pack 2: The newest addition the GMAT preparation library released in March 2016 these are two official GMAT practice tests brimming with Official GMAT questions and powered by the Official GMAT algorithm. A GMAT prep essential. Here are some recommendations for studying with Exam Pack 2.
GMAT Simulated Booklet: On the GMAT you are not allowed any scratch paper. You are given a 10 page plastic pad and marker. Ideally - do all of your practice tests using the pad. It is a bit different than using scrap paper. We have created a replica of the GMAT pad including the exact markers that you will be given at the test center.
GMAT Question Pack 1: A question bank of 400+ official Quant and Verbal questions. This software let's you build question sets based on question type and question difficulty. I like Question Pack 1. It's a great value and a valuable resource to use towards the middle and end of your GMAT preparation. Here is an in depth review of the GMAT question pack along with some suggestions on how to get the most of the question bank.
GMAT Focus: These GMAT CATs are controversial because they are so damned expensive.These are great GMAT resources for the last week before the big day. The GMAT focus four pack has four 24 question CAT quizzes. The question difficulty and feel is very similar to the most recent official GMAT exams. Here is a more in depth look at GMAT Focus.
GMATPrep Tests: The GMAT prep tests are the closest you get to the real thing. These GMAT tests are the holy grail of GMAT prep. Almost identical in feel to the real GMAT exam. The newest version of the software includes integrated reasoning. You get two separate CATs which draw from separate question banks. Not, to mention these GMAT Prep tests are FREE!
GMAT Paper Tests: These are official GMAT tests from when the test was on paper (and easier). These are often ignored but they offer great GMAT verbal practice. I have found the verbal score on the paper tests to track official verbal scores. The Quant is too easy unless you want to use it to brush up on the basics.
GMAT Enhanced Score Report: This is a product that you can buy after you have taken your GMAT in order to get more information about what went wrong on the exam. For most people this is a waste of money. Here is a GMAT Enhanced Score Report review with some suggestions on how it can be useful.
OLDER GMAT BOOKS
The GMAT Official Guide 2016: The GMAT Official Guide for 2017 is now out so the 2016 guide is no longer the freshest of the fresh. But, if you already have the 2016 guides or can get them dirt cheap, no need to buy OG 2017. It only has 15% new content. Here is an in depth review of OG 2016. I would recommend getting the digital/kindle edition so that you always study with a screen instead of with paper. To save a little money grab the bundle of all three Official Guides for 2016.
The Official Guide for Quantitative Review 2016: This is the updated version of the Quant review 2nd edition. Again - if you already own the 2nd edition then you should be fine sticking with it. However, if you are buying new definitely go for the 2016 edition. Here is a breakdown of the Quant Review 2016.
The Official Guide for Verbal Review 2016: This is the updated version of the Verbal 2nd edition. Same advice as above. Here is a breakdown of the Verbal Review 2016.
The Official Guide 13th Edition: The OG13 is now outdated. It is still fine to use if you this is the books that you already own but if you are going to be buying a new book go for the OG 2016. I would recommend getting the digital/kindle edition so that you always study with a screen instead of with paper.
The Official Guide for Quantitative Review 2nd Edition: Not the most challenging of GMAT books but a solid math skill builder. These questions tend to be easier than the official guide but are still worth doing especially in the beginning of your GMAT preparation. Get the kindle/digital version.
The Official Guide for Verbal Review 2nd Edition: Solid GMAT verbal practice. I find this book to be a bit easier than the official guide but it is still excellent supplemental practice that you can use at the beginning of your GMAT preparation or for extra practice questions down the stretch. Get the kindle/digital version.
Whenever I want another opinion on a question I take a look at several explanations across forums so that I get a cross-section of ideas. Google the first several words of any official GMAT question and you should get a result from at least one of these forums.
GMATClub is a great place to find explanations for official GMAT questions. Lots of people post here so not all the explanations are great. That said, with some patience you can find some excellent explanations from some very smart people. The other great thing about GMATclub is the wealth of materials and guides in their archives. Same with the explanations: not all of it is great. But, if you take some time to sift through the materials you can find some real gems.
BeattheGMAT is similar to GMATclub and also has a lot of GMAT explanations. There are some good explanations here as well although I find myself leaning more on GMATclub and ManhattanGMAT. That is a completely personal thing and I would encourage anybody doing self-prep to check out all of the sites and figure out what works for you.
The ManhattanGMAT forum is a great place for GMAT explanations. Here you probably get the most organized forum as there rules for posting are pretty strict. You also get a lot of responses from Manhattan GMAT instructors. Along with that you get a bunch of great information but a forum that could be biased towards a specific approach.