What’s Good about Barron’s GRE

Compared to most of the prep books out there, the questions have a greater verisimilitude to actual GRE questions. Many of the Text Completions and Sentence Equivalence are not overly straightforward; they do require some thinking. Also, most of the vocabulary is typically what you’ll see on the GRE.
The reading passages can be quite challenging, though the questions tend to be more straightforward and less tricky than actual GRE questions.
The math questions are fairly representative of what you’ll see on the actual test. I did not feel that they were nearly as tricky as actual GRE questions though. So for practice, the questions are helpful, but to really hone one’s chops one would be better served with Manhattan GRE online practice tests or Magoosh.

The Bad

TC/SE
While the TC/SE questions are pretty good, they are not up to GRE standards. The sentences/paragraphs may be long, but I wouldn’t necessarily say they are convoluted or as artfully crafted, i.e., it’s not difficult to figure out what word goes in the blank. The level of writing isn’t always as sophisticated as that found on the GRE, so you aren’t necessarily flailing about trying to make sense of the overall meaning.
These are quibbles, and really the thoughts of someone who is spent too much time analyzing and writing Text Completions . Most of the questions are definitely still helpful and won’t hurt impair your ability to solve TC’s, the way doing Kaplan TCs could.
A few questions though have questionable answers. Notably, some Sentence Equivalence questions have credited answers that end up creating different, not synonymous, sentences. These are rare, though.
So if you are looking for more TC/SE practice material, and you’ve already gone through the official guide, powerprep practice tests, Magoosh practice questions, and Manhattan GMAT online practice tests, then this book and Barron’s GRE are your best bets. Altogether (including both SE and TC), there are about 100 practice questions of okay quality in each.

RC
Some of the passages are very dense and difficult. Others are quite straightforward. Some passages are far, far longer than anything you’ll see on the GRE (800 words vs. 450), and even these passages have only three, not the requisite four, questions.
What does this all mean? Well, the test is not really well standardized. To exacerbate this situation, even the TC/SE questions are not of similar difficulties throughout the sections. So sometimes you’ll get a very difficult section with a super long reading passage and other times you’ll get a much easier section.

Overall

This flows into my biggest criticism of this book: you shouldn’t use it for its intended use, i.e., as a resource for full-length practice tests. And this point is no mere quibble. If you adapt your timing strategies to accommodate a massive passage, essentially rushing through other questions, you won’t get a feel for pacing on the real test. And anyone who has taken a few practice tests—if not the actual test—knows how important pacing can be.
Also, since the quant section tends to be easier, I don’t think this book offers you a sense of what it is like to take a full-length test.
So what do I recommend this book for? As a pretty solid question bank from which to practice.