Comparisons between this and Lemony Snicket will be omnipresent. This is unfair. Aside from orphans and evil adults, these really have little in common.
Snicket fans will enjoy this, though, as will any child with a good background in the Orphan Oeuvre of children's literature. The Willoughby children, however, want to be orphans because their parents are so nasty and uncaring. Luckily, before their parents leave on a world tour, they hire a nanny who turns out to be very nice, as well as a good cook. Their house is sold, they move in with a lonely neighbor who has adopted a foundling, and inevitable coincidences occur.
This does threaten to be a book that is hard to describe. Lowry has her tongue firmly planted in cheek throughout, but in a fun way. That Lowry enjoyed writing this, and thought a lot about the literature that was part of her youth is very evident. There is a nice glossary at the end, and brief descriptions of books about orphans, which may well entice children to look for them, although finding a copy of Toby Tyler may be difficult. The cover art appeals to me, but looks a lot like the 70s-recalling-the-Victorian-era art work that I am currently pulling for lack of circulation.
Since this author has such a following for high quality, diverse body of work, this is a book that just about every elementary and middle school library should buy.