All of these books are books or series that have no sequel or continuation planned by the publisher but that the authors have all stated that they are still interested in continuing or finishing.
Heist Society series by Ally Carter – Ally has finished out her spy series Gallagher Girls and is embarking on a fun new series, Embassy Row, but I hope to hear more from her group of charming rogues and delightful criminals. There is a lot of story left there!
Dreamdark series by Laini Taylor – This MG offering from acclaimed YA author was left abruptly hanging at the end of the second book and I would love to see the conclusion.
Academy 7 by Anne Osterlund – This was the first book in a planned trilogy and please can we have the remainder of that trilogy now? Please?
Princess Curse by Merrie Haskell – There was so much left open and unresolved at the end of this fairytale/mythology/fantasy debut.
Ordinary Magic by Caitlen Rubino-Bradway – This funny, enjoyable debut is set in a world where magic is the norm and those without it are the outcasts. It is great and I cannot wait to hear more.
Castle of Shadows and City of Thieves by Ellen Renner – This really just needs a conclusion to tie up the storylines and character arcs.
Alcatraz by Brandon Sanderson – #5! I know that he finally got the rights back to it but he has an enormous list of titles to be published/that he is working on, so it may well be years before he gets around to publishing this although I believe that it is all already written?
Queen’s Thief series by Megan Whalen Turner – The next book (and the sixth too), please?
This is just my own personal list – What series do you want to see finished? What books need a sequel?