The afterword by Koontz includes passages explaining the revisions of the original novel.

“The Key to Midnight was the first novel that I wrote under the pen name Leigh Nichols, which I now no longer use.  The other Nichols novels included Shadowfires, The Servants of Twilight, The House of Thunder, which have previously been put under my real name, and one other that will be reissued in paperback in 1996.”

“…I’d cut 30,000 words from it, added about 5,000 new words, and reworked it nearly line by line.”

New dedication: “This better version is for Gerda.  I can go back and improve the earlier pen-name books  but I’m afraid I don’t have enough energy to make all the desperately needed improvements in myself!”

Also, check out this blog post regarding my thoughts on the POD edition.