Red Cloaks And Underground Princes

I've been going through my Rambling and Future Reading pages trying to clean it all up (more on that tomorrow) when I realized I never did a rambling on Princess of the Silver Woods by Jessica Day George, the last book in the Princesses of Westfalain series and that just won't due.  So without further ado, as always SPOILERS AHEAD!

In this book we see Petunia, the youngest of the the 12 sister princess almost all grown up.  She is in her way to go visit a relative when she is held up by bandits in wolf masks.  Petunia (with her red velvet cloak) soon discovers that the head of these wolf bandits is actually a young earl by the name of  Oliver.  Turns out that during the brutal war that we learn about in the first book the earl and his family lost their home through what turns out to be treachery.  Petunia is sympathetic but eventually continues her journey.  While at the Grand Duchesses house, Petunia and her sisters are soon caught up in a hellish nightmare come true, when it is finally revealed that the Grand Duchess is actually one of the Nine Daughters of Russaka which are rumored to have given birth to the King Under the Stones sons (this makes a lot more sense if you have read the other books).  The Duchess is now trying to get the 12 Princesses back to the underground world of the dark princes, to fulfill the intent of them all getting married.  The girls, their husbands, boyfriends, and friends all fight back with various magics, of course overcoming the bad guys in the end.  Oliver is restored to his earldom and he and Petunia have a thing and everybody appears to live mostly happily ever after.

Ok Ok, I know that is a super chintzy recap, but really that is all that happened.  Over all the book was supposed to allude to the tale of Little Red Riding Hood, but mostly felt like a rehash of the first book.  This time around the girls were better prepared, and much more knowledgeable about the underground horror's...but I don't know, it seemed a bit redundant.  As with the earlier books, I do appreciate the self sufficiency of all the girls, their ability to knit, sew, read, write, cook and persue their own interests is a refreshing change of pace for a typical princess.  I also enjoy the sheer number of princesses/sisters in that no single one is a super special, treasured, pampered only child, again a different take on your classic princess tale.  This book would be pretty difficult to understand if you had not read the other two, so keep that in mind.  Eh I know this short for a rambling, but there you have it.  This was not a bad book, just a bit flat compared to the other two.  Overall I give it a 6 out of 10 red velvet cloak and appreciate it for wrapping up the story in a neat little package.
How do you feel about the varying degrees of success of a book through out a series?  If a book pays homage to a well known story, how recognizable does it have to be?  How much of a cop out was this rambling?