You're doing great, so in addition to those books I suggest a two-hand approach: Error Log review, and Careful Strategy!
Moving forward, anytime you get a Quant question incorrect, add it to your Error Log. Here's some help to get started:
https://www.beatthegmat.com/mba/2010/11/ ... -error-log
The idea is to start tracking WHY you get Q's incorrect. If you were indeed laughing your way through Kaplan and OG, then your Math skills are probably there. You can also use the Error Log to pinpoint weaknesses in some of the less often tested concepts.
For more Q's, I suggest Grockit (but of course I am biased). You can use a free trial membership to scope out some of the harder Q's in our question bank. They are mocked from the OG and GMATPrep.
In terms of "Careful Strategy" you can probably afford to slow down, and be more measured in your approach. Different types of questions require unique strategies. Some basic tips:
It may sound obvious, but don't make assumptions about unknown quantities on the GRE. "Numbers" can be positive integers, negative integers, decimals/fractions, or 0.
Slow down on Word Problems. Make sure you really understand the concepts underlying the question. One or two words can radically change the question. Don't rush these challenging questions, even if the math seems fairly obvious!
Watch out for extra steps. You may need to find 1/y, instead of y. Or you may be asked about the "ratio of girls in a class to boys in a class," but have to solve for the two parts of the ratio first. Pull out the important info first. Write down any key numbers, variables, or phrases from the question and write them down on your scratch pad. This is the step most students skip. Don't just scan the screen and start solving. Forcing yourself to slow down and process each piece of information will give your brain time to sort through it. This may lead you to find a faster way to solve!
Backsolve more when there are numbers in the answer choices. Sometimes just doing the algebra will be the simplest way to the get the correct answer, but backsolving is a great strategy to check your work as you go. Go through the answer choices and plug each one into the question.
Pick Numbers as much as possible. Substituting abstracts like "x" for easy-to-worth-with integers like "2" and "3." Keep the numbers small and make sure they are allowed by the definitions in the question.
Be more measured in your approach than you think you need to. Evaluate the question from ALL angles before deciding whether it seems easier for you to do the math traditionally or use a specific strategy. When you are practicing Problem Solving, try solving the same question in more than one way to see which was faster and more effective.
Remember that "Y/N" and "Value" Data Sufficiency's are different. For "value" questions, a statement must provide a single numerical solution to be sufficient. For "yes/no" questions, either a firm "yes" or a firm "no" is acceptable but a single statement cannot be answered both ways. For "yes/no" questions, it doesn't matter how the question is answered, just that it can only be answered in one way.
