Book of Night with Moon is a cat book for those who grew up with Diane Duane’s So you want to be a wizard series. It is somewhat dependent on the earlier works, even though it is not explicitly a part of the same series (and the plot itself stands alone).
Those with cats as pets will delight in the detailed and surprisingly well rendered view into the mind of a cat, where playfulness and feline politics vie with the weighty concerns of world-saving. Those without cats will be lost and confused, which is perhaps typical human behavior from the perspective of a cat anyway..
Unfortunately, this book isn’t as good as those that came before. The cat angle is a saving grace that will provide ample amusement well worth the purchase price for those who like that sort of thing. Those who don’t should pass.