I admit that I approached this book because of the cover and because of my interest in henna. Scribner offered an early look and I took them up on the opportunity. If you're also intrigued with henna, you'll find some history and symbolism and magical-realism sort of association with the subject in this novel.
You'll also find an interesting history of Jewish families in Yemen in the early 20th century. I feel my education in these areas, in general, is sorely lacking and so much of it was new to me (though it appears to have the same novelty to other reviewers).
I enjoyed the first and last quarters of HennaHouse the most, though it does feel that the general tone of the book shifts halfway through. The scope is wide: family, love, betrayal, fascinating laws and rituals.