(Taken from
http://www.linguistics.ucsb.edu/faculty/bucholtz/sociocultural/bookreviewtips.html)
Why write a book review?
There are several reasons why you should begin writing book reviews early in your graduate career.
To make a contribution
Even students just starting out in graduate school can often provide very thoughtful evaluations of published work in their area of interest and knowledge. It's important for you to enter the intellectual discussion as soon as you have something to say, and book reviews are one good way to do this.
To perform an academic service
Book reviewing is a valuable service to the academic community, and it's worth getting familiar early on with a task that you'll probably continue to perform throughout your academic career.
To beef up your CV
Book reviews give you a chance to strengthen the publication section of your CV, especially before you're at the stage of your career where you're ready to publish your own research. Although book reviews aren't weighted as heavily as original research articles in hiring and other personnel decisions, they do have some value, and a book review or two will help you begin to develop your CV.
To learn how to write a book
One of the most effective ways to master the conventions of academic writing is to read closely and analytically, the way you need to in order to do a book review. In preparation for writing your own first academic book-length manuscript--your dissertation--it's extremely useful to get a clear idea of how an academic book is put together by looking at some examples in detail.
To read
Most academics, including graduate students, never have enough time to do all the reading they want to do in their field. Doing book reviews gives you an excellent excuse to read books of interest to you and helps you keep on top of current trends in your field.
To get a free gift
A not inconsiderable factor in deciding to do a book review, especially when you're a penurious graduate student, is the added benefit of receiving a free book as compensation for your time and expertise. Academic books can be quite expensive, and receiving a free copy of a book of interest to you (typically in hardback) is a very pleasant bonus for doing a book review.
To become known in your field
Perhaps the most important reason to do book reviews is that it brings you into the scholarly conversation and allows you to make connections with other scholars. As a reviewer, you'll gain attention from the author and from journal readers as a new voice in the field. You may even hear personally from the author (if your review was especially positive or insightful--or, unfortunately, if it was especially negative or clueless, at least in the author's view).
If you submit a well-written review within the deadline indicated by the editor, you may also become a valuable reviewer for the journal. Soon, you may no longer need to offer your services as a reviewer because you'll be receiving requests from editors to review books for them. Having a good relationship with a journal editor as a book reviewer may also help ease the way a bit when you're ready to submit a manuscript on your own research to the journal. In academia, as in Hollywood, it's always better to be known than unknown.