We purchased the audiobook version of this book. It was an interesting story that my 8 yo loved, but my 6 yo was somewhat frightened by it(and he's not frightened by much lately). The characters are very interesting,  deeply drawn and the relationship between the "good" twin  (Angela) & "bad" twin (Diabola) is complex & rich. The  reader did an excellent job (very important in an audio book). In  addition, the layers of the story were sufficient for my husband & I to  enjoy the book as well (we listened on a long car trip). The only reason  I gave this 4 stars was the fact that my 6 yo was too young for some of the  content, making this book not appropriate for all ages
The characters are very interesting,  deeply drawn and the relationship between the "good" twin  (Angela) & "bad" twin (Diabola) is complex & rich