People can and do find success both ways. So whatever works best for you is fine. With that said, The CR Bible really is geared to the LSAT and can be a little confusing for the GMAT.

On the GMAT I believe you should read the question stem first.

When you do read the question stem there is really one thing that you are looking for -- does the stimulus (passage) have a conclusion?

Because the most important thing you can focus on in the stimulus is the conclusion it is important to know if there is in fact a conclusion in the stimulus.

If you find that you have a strengthen, weaken, bold-faced, method of reasoning, etc. then you do have a conclusion in the stimulus.

If you have an inference/conclusion question or a paradox question you should not be looking for a conclusion in the stimulus.

So both things are partially right. You should read the question stem first, but you do not want to be too focused on what you are trying to do as you read the stimulus. Pay attention to the stimulus and really just focus on identifying the conclusion - which is after all the most important thing.

You may be confusing critical reasoning and reading comprehension.

In critical reasoning you need to read the stem first so you know what you are looking for. If you read the question after you read the stimulus you will have to go back and re-read to find the specific answer...a waste of time.

In reading comprehension, you are dealing with five to eight questions relative to a passage. Most people cannot hold all those questions in their head and still read the passage efficiently or effectively. You are better served to read the passage strategically, building a clear understanding of the topic scope and purpose and noting where in the passage you can find the relevant information once you attack the questions.