"Oliver's characters leap off the page and readers of all ages will find themselves eagerly rooting them on and clamoring for more as their story ends. Hand this to fans of adventure, magical creatures, and epic quests." - School Library Journal (starred review) "In this grimy, Dickensian world, an alternate-history Gilded Age, vast wealth coexists with grinding poverty and fear of the other runs deep: Where fear rules, difference is the enemy. The monsters are standouts, manifesting, like all animals, unique natural attributes and proclivities (described in a comprehensive guide). Charming or alarming, these creatures and their world, rendered in abundant, imaginative detail, beg for further exploration." - Kirkus Reviews (starred review) "Oliver's imaginative story combines exquisite descriptions with a spirited narrative, and readers will delight in the quirky creatures and settings." - ALA Booklist "Oliver's marvelous historical fantasy hits just the right tone of sincerity and whimsy; alongside weighty themes 'of violence, of hatred, of cages and isolation,' an excerpt from A Guide to Monsters and Their Habits describes many of the beasties in enough detail to ground the premise and bring the monsters to life, and occasional illustrations by Aldridge give a realistically fantastic feel to the meaningful text." - Publishers Weekly (starred review) "Oliver retains a keen sense for the emotional dynamics of pre-adolescent girl friendships.

The recurring meditations on the true nature of monstrosity and the unjust devaluing of lives may offer routes into timely conversations about the lives our own time devalues." - Bulletin of the Center for Children's Books "Oliver's wordplay is often clever ("the daylight.was starting to seep across the cluttered countertops like the drool of a Mattahorn salivus"), and her collection of monsters is creative and thorough. Cordelia and Gregory face instances of peril that are exciting without feeling too dangerous, and the book's secondary characters, both human and monster, add much to the story." - Horn Book Magazine.