Entwined is presented two ways - a sash dance in which the man tries to "entwine" his partner by the end of the music and in the malevolent magic that lies dormant in this retelling of the Twelve Dancing Princesses.
Dixon gives her retelling considerably greater background. When the Queen dies at Christmas, giving birth to her twelfth daughter, grief splits apart the King and his daughters. He is devastated and doesn't want to talk about his wife. The girls are ordered into mourning for a year - no going outside, the draperies are closed to shut out the light, all the girls' dresses are dyed black, the clocks are stopped, and there is NO DANCING (dancing was an activity their mother loved, making her death doubly difficult). When the King leaves for the war front, Princess Azalea (the eldest princess and heir) and her sisters feel abandoned.
By happenstance, Azalea finds a magic passage (opened with Mother's silver handkerchief) leading to an enchanted crystal world minded by Keeper. Keeper is handsome and genteel and allows the girls to come dance every night. In an act of defiance, the girls become the Twelve Dancing Princesses of fairy tales. It is their Secret, sworn in silver...until Keeper lets on his secret. It is dark and deadly indeed.
The story has a very British-Victorian feel - Azalea is in some ways an analogue to Queen Victoria - although it is set in a make-believe European country. There are lots of cute, funny bits involving the younger sisters and the suitors who come to court Azalea (balancing the darker aspects of grief and revenge). While Azalea is talking to her (obvious, to all the readers) Prince Charming, she wants to give him toast - it's such an innocent component to "I think I love him" but it expresses far more care than teen love usually does.
As a dancer, I loved the endless different social and group dances Azalea teaches the sisters - walzes, schottishes, reels, tarantellas - on and on across different countries and time periods. It's a part of dance history that so often gets lost so it's nice to see the brief mentions throughout the book.
I had quite a fun time with this book and it was perfect for snuggling up as the nights grow cooler.