Sometimes it is difficult to find a book review -- the book may be very old, very new, not widely distributed. In addition, many more books are published than are reviewed. If that happens, you can stilI make a reasonable, responsible purchasing decision.
Unless the book is the first book the author has published, return to the standard reviewing sources you have already checked. This time search for the author and do not include the title you are looking for. Read reviews of the author's other books. If they are overall positive, it is reasonable to purchase the new book by this author.
Particularly if the author has not yet published widely, biographical material about the author, and his/her background, can also help you decide. Try biographical sources such as those found at: https://www.lib.ecu.edu/databases/tag/biography
Something About the Author Online is helpful for authors of children's and young adult authors.
The quality and reputation of the publisher can be determined in a variety of ways.