Your Thoughts on Favorite Sequels

I'm in writing mode again - working on the THE TORN WING, which is the sequel to THE FAERIE RING.  As the flap copy on my website reads:  Return to Victorian London as sixteen year-old Tiki is drawn into an ancient battle between the seen and unseen worlds. Can't give away too much, right? ;-)

As a reader, I have my opinion on sequels - I can think of some that I loved (every Harry Potter book, two of the three in The Thief series by Megan Whalen Turner) and some that I have found disappointing, either because they are just book one written over again, or I don't see enough of my favorite character.

As a writer, I approach a sequel from a different perspective. I have an overall story arc in my mind that not only spans the book currently being written, but also the book before and potentially one or two books after. To accomplish that, sometimes the main characters from the first book are not needed, or can't be present, in every chapter as the story moves forward. New characters have to enter the picture.

So the question is how to write a sequel that is as engaging and entertaining as the first book? The trick, I guess, is to make the new characters so interesting that the reader wants to know what happens to them as well as the main characters.

It all sounds so easy when put that way, doesn't it? ;D

So tell me - what do you look for in sequels? And tell me the names of some of your favorite sequels and why you liked them so much.

Thanks!
~Kiki