These are some reliable professional review sources. The writers working for these sources have professonal training in the fields of literature and education, and judge books on quality and their general appeal, not on their own personal tastes.
School Library Journal
VOYA (Voice of Youth Advocates)
The New York Times Book Review
There are many others . . . but be careful! Make sure the author or organization has expertise about literature for young people.
You may use these sources as background information for your own purposes, but do not choose them for your cited reviews, or quote them on your final project.
Publishing companies (Scholastic Magazine may be an exception, especially if books are from a different publisher)
Author websites (great for background research, but not unbiased information about books!)
Personal blogs, tubmlrs, etc. . . . there are an endless number of these! Even self-published blogs by librarians, teachers, etc., are often too informal and too personal to be considered credible reviews.
Some review sources have "appropriateness for audience," or a specific focus on promoting a certain set of values, in ADDITION to quality, as part of their criteria for evaluating books. It is fine to use one of these sources if you are aware of the site's purpose and intended audience.
Common Sense Media
Focus on the Family