As an author, I like to be part of a writing community of authors supporting and helping each other. What better way to build a network of like-minded individuals than to help each other grow? Reviewing is one such process.
There are a few things to keep in mind when reviewing a book:
1)What kind of book review is it - do they want an extensive review or just a blurb?
2)Where will the review be submitted to? - on the author's website only, or on Amazon.com, etc?
3) There may come a time when reviewing an unpublished book in pdf form that you might see errors. It is all right to approach the author and ask if they'd be interested in having you make comments in the pdf file. If they agree, just click on the comment icon and it will open up on the side of the page. Type your comment, then click the x. It will store the comment. Then save the pdf file under a revised name.
Besides helping the author with your review, when you sign your name at the end of the review (your name and the name of your book), that is an easy way to promote yourself and your works.