When you are in a place where you want to write a book review, you will be sharing what you know and feel about the book with your readers.  Writing a good book review is not necessarily something that is instinctive however, so make sure that you take some time to consider some points that will make your review more engaging and more useful to your audience.

First, consider the book as a whole.  Who is the audience that is being marketed to, and are you that audience?  Why did you pick up the book in the first place, and what is the packaging trying to tell you?  Consider what sort of story that you expect from the packaging that the book is in and make a note of it.  When you have read the book, you'll find that going back to this guess can be an interesting thing to include in your review.

As you read the book, make sure that you read it critically.  While there is nothing wrong with reading a book just to enjoy it and without much consideration, this is not the way to read it if you are planning to do a review of it!  Ask yourself questions and figure out what the author is trying to say.  Consider the points that the author is trying to make.  What kind of world has he or she built and how does it comment on the one that we live in?  While this is especially true when you are reading speculative fiction, you will also find that it is quite true when you are thinking about mainstream fiction as well.  Question things like world-view, the prejudice of the characters and how gender and sexuality and race are all being portrayed.  This can help you get some insight into the book and add another layer of meaning to it.

When you go to write the book, start by introducing it to your audience.  Assume that they have never seen a copy or heard about it before and tell them a little bit about the author, what other work they have done and how the book is presented.  Tell them what the book is about, and briefly summarize the book.  Remember that you should never give any more information about the plot than is on the back of the book; giving your audience spoilers on content is going to make them quit reading fast.

Give your reactions to the book.  Be balanced and fair, and if you have specific biases, it is always good to let the audience know.  Remember that you are not necessarily trying to get the audience to read a book or not to read it; instead, you are giving them information so that they can decide for themselves.  How did the book make you feel, would you read more by the same author?

Book reviews are an important way to share your views on books with others and to introduce people to literature that they might never have stumbled on on their own.  Write your book reviews with care, and you'll find that there are many people who are eager to listen.