I think I've mentioned before that when it comes to reviewing a book for my kids, I often use Common Sense Media. It has tons of movie, game, music, and book reviews that spell out what is in the content of each with a seemingly unslanted view. Also, fellow users can also post a review or comment of the same material so you can get an idea of what other kids and parents think of the material. Very helpful.
While snooping around on a homeschool forum, I found mention of another book review site, Squeaky Clean Reviews. These are reviews of books from a Christian perspective. After looking through the site, I thought it worth a mention.
Books are listed in alphabetical order so finding a review is pretty straightforward. Though, a pet peeve of mine, if the title starts with "The" expect to have to look through the "T" section. The reviews contain information on different aspects of a book including the plot, morality, violence, drug and alcohol content, sexual content, and cruel or profane language or content. Then, based on the review, the book is given an overall score on fun and values.
My impression of this site is that I find it helpful and will most likely consult it the next time my kids ask me about a book I know nothing about. I appreciate that while the reviews do address areas I have concerns over and that the reviews are done from a Christian perspective, they aren't "preachy" or seek to wag fingers at anyone for a reading choice (at least the handful, of reviews I read).
The site does have its limitations, though. The database is still a bit limited. As more people come forward to write a review, this will change. (Reviews are submitted by volunteers as well as the site owner. See the website for more information.). Also, only one review is submitted per book. This helps avoid confusion from opposing reviews, but it also means a lack of viewpoints on the book. While the reviews are supposedly from Christian readers, there's no guarantee that any reviewer will have your exact set of values in mind when writing their piece. You really can't expect that from any site. I tend to lean on the side of sifting through a number of reviews to see if there are conflicting reports or a theme of concerns that crop up. With only one review allowed per book, this limits my information gathering. However, if you know of concerning content that was left out of a review, you can contact the site and inform them. The site states that they will then consider revising the review.
Overall, I think Squeaky Clean Reviews is worth a look when deciding on literature for the kids to read.