I found this to be a truly satisfying historical fantasy. It has scary bits, funny bits, and thoughtful bits. It has a great central character, who's both believable and likable, and a nuanced supporting cast (including adults who are interesting people too!). And it has a really good story.
As an impoverished (but plucky) Victorian orphan, Birdie knows what it's like to live on the edge of nightmarish destitution. So she considers herself fortunate to be the apprentice of Alfred the Bogler. Sure, she's the one who baits the bogle traps, siting in an unfinished circle of salt and singing to lure the bogle out of hiding. And yes, the reason bogles need dispatching is because they eat children. Alfred, though grumpy, is not abusive, and the money, though not enough for much in the way of creature comforts, keeps them going. They are a good team.
In this alternate London, the educated rich consider bogles the childlike superstition of the lower orders. But there are two who don't. One is a well-off woman engaged in the academic study of supernatural creatures of the British Isles, keen to use Alfred and Birdie as a means of observing the creatures first hand (which leads to amusing situations in which she is desperately out of place), and, as the story progresses, keen to introduce science into bogle trapping and save Birdie from danger (though Birdie is hostile to this idea, as it would put her out of work...).
And then there is the second well-off person who believes in bogles...who doesn't care a whit how many children they eat. He, too, is keenly interested in Afred's bogling skills, but his interest is much, much, more dangerous than any monster Birdie's ever faced.
If you are looking for books for young readers of fantasy of the alternate worlds/quests/heroic kids saving the day with magic who are reluctant to try anything real world, or historical, offer them this one. They'll get a nice introduction to Victorian London along with the brave kid, the magic, and the monsters.
I enjoyed it lots myself, and highly recommend it to both kids and grown-ups. Perhaps more to the kids, because it is written with them in mind. There's a nice solid simplicity to the progression of the story which makes is very satisfying. Though pleasing complexities of plot and character are introduced, they are done so without any teasing of the reader. It's a complete story in its own right; the ending is an ending, though there's room for more fun with bogles.