How do I get my book reviewed? First, you've got to learn something about the physics of publication, and the simple fact that magazines and newspapers work ahead of time. The publishing process involves many steps (writing, editing, designing, selling ads...) each with its own due date. These deadlines are set in an editorial calender, determined by the Big Kahuna of deadlines: the date that the printer must receive the final proofs in order for the March issue, say, to be printed, and sent to subscribers and newsstands, by March. Each department (sales, art, production, editorial) works backward from this deadline to set all the other deadlines. And hidden in these compounding deadlines lies the secret to getting your book reviewed.
Here's the two-pronged take-home: 1) It takes a minimum of four months "lead time" for a review (or any article) to go from assignment, through writing, editing, rewriting, designing, proofing, and printing, to bound, boxed, and delivered to stores and subscribers. 2) Most magazines only want to cover new books, and by "new," they mean books published the same month as the issue of the magazine.
So, if your book is due to be published in August, and a magazine starts assigning articles for the August issue five months earlier, in March, how can your book possibly get reviewed? Given the physics of time and the fact that it doesn't run backward, the book has to come out ahead of itself. This time-space conundrum is solved by the pre-press galley or Advance Review Copy (ARC). Four to six months before the book comes out, the book publisher releases a limited number of ARCs on cheap paper with a mock-up paperback cover (because the real one isn't usually designed yet), and sends them out to editors at magazines and newspapers. ARCs also serve as a convenient way for the author, editors, and designers to do a final proofing, but they are an absolute necessity to getting your book reviewed in most national or regional print publications.
The rules differ for online reviews (since it takes much less time to go to "print" digitally) and for smaller or local publications less concerned with being right on top of the news. Also, since printing ARCs takes money and forethought, some publishers cheat by just printing manuscripts, bound or even un-bound, and sending those to reviewers instead. Then again, some reviewers don't like to read these manuscripts because they are awkward and messy compared with galleys. (You can check the submission guidelines or ask editors whether they'll accept a bound ms, and how long is their magazine's lead time.)
All-too-common scenario between Excited Author or book publisher and Seasoned Reviewer or magazine editor: EA: "Can I send you my book to review?" SR: "When does it come out?" EA: "Next month!" SR: "I'm sorry that's too late." EA: "It's not even out yet and it's too late to review?"