Caster Chronicles, #2.5. ebook. Published 2011.
“Dream Dark” tells the story of how Link slowly came to the realization that he was an Incubus. Since it only took a few pages to do that, his discovery is followed by chapters from the Caster Chronicles of his visit to Macon seeking advice and his trip through the tunnels. The mini, mini short, short story ends with a few chapters from “Beautiful Chaos.”
Thus, with only a few new pages in the entire ebook, I wouldn’t recommend buying it as the information comes from previously released books. I’ll leave it up to you to decide if you want to Read It Or Not.