I define mash-ups as classic books rewritten to include new paranormal elements. These can usually be identified by a classic author's name included with the writer of the new material. The story is the same as the original; new paranormal material is added. Mimicries are stories written in the style of a classic author and include prequels and completely new stories.
Twisted histories are defined, by me, as novels wherein an historical figure is now fighting against or dealing in some way with paranormal creatures.
Finally continuations are just that - a continuation of a classic novel with the addition of paranormal elements if they were not already in the original book. Alternates are simply a classic story told from a viewpoint not in the original book and again with paranormal elements if they were not in the original book.
Of course in many instances these categories overlap.
I've collected a list of quite a few of these books published in 2009, 2010 and 2011. I'm sure that there are books missing. This list will be updated on an ongoing basis.
MASH UPS and MIMICRIES
Louisa May Alcott
L. Frank Baum
Daniel Dafoe and H.P. Lovecraft
Sir Arthur Conan Doyle
CONTINUATIONS and ALTERNATES
ONE LAST THING: I include the following book because it is, in part, a send up of all the Austen mashups: