There are a number of reasons one might write a review of a book. Most of these reasons aren't all that helpful when it comes to Gravity's Rainbow.
One reason is to provide potential readers with a sense of the book (plot, structure, style, characterization). The best way to get a sense of Gravity's Rainbow is to read the first page. It basically goes on like that for another seven or eight hundred more.
Another reason is to enlighten the world with your sparkling insight into the subtlties of symbolism and layers of meaning in the book. With regard to Gravity's Rainbow, you can save that stuff for your weekly book club. The symbolism and layered meaning in GR are about as subtle as a rocket attack on a movie theater. This is why GR is often compared to Finnegan's Wake. If you've ever watched Joseph Campbell explain that novel, you realize that the search for deep intellectual insight is a conceit. These novels require your best effort just to understand the LITERAL stuff.
Another reason to review a book is to provide your own subjective opinion about the overall quality of the experience. I've found that many such GR reviews fall into one of two camps: "I read 'X' pages and couldn't/didn't finish it" or "Thomas Pynchon is God". The problem with reviews like this is that they say more about the meta-experience (sorry, but that is the appropriate word) of reading the book than they do about the book itself. Those of us who finish it are subject to a kind of "Iron John" machismo which falls apart if we are forced to admit that the whole thing might be a colossal put-on. On the other hand, those who give up can't help feeling that perhaps they are missing the big IT and don't like feeling that they might be unable to appreciate genius.
So is it the Emperor's New Clothes, or Pearls Before Swine?
It doesn't matter. The question is probably meaningless anyway.
If you like incredibly obscure cultural references, if you like dense imagery, if you like chilling portrayals of paranoia and the dire consequences to humans when people with power succumb to it and if you like conspiracy theory, you'll dig this book.
I do, so I did.
On the other hand, if you're hung up on little things like narrative structure, characterization, plot, etc., I'd stay away.