Modern book about OCD and Alternate Worlds

I remember seeing a blurb about a book where the main character (adult) was OCD about certain routines. The odd thing was that these routines were actually necessary as a type of world maintenance, to keep him in the same world. If he missing something, then things changed dramatically. It seemed modern urban.

I believe it was geared towards adults rather than kids. I thought it was published by Baen, but I can't find it among their listings.

Edit: Dates likely 90s or 2000s, but anything earlier on the topic would be interesting too. :)

Could it be maybe Wicked Game?

It doesn't seem to really match your description - the OCD apparently isn't central to the story and it's a book about vampires, which you would probably have remembered, but the author explains her reasons for giving the vampires OCD here:
http://patricias-vampire-notes.blogspot.com/2009/06/ocd-and-vampires-by-jeri-smi...

"As I began the first draft of Book One in the series, Wicked Game, the vampires' OCD behaviors were just a schtick, a source of comedy or character idiosyncrasies. Then one day in the middle of the second draft, it all came together for me.

As I mentioned above, the vampires in my universe are "stuck in time," trapped psychologically and culturally in the era in which they were made. They require both a tie to their original "Life Times" and a tie to the modern era to keep them from "fading" into mindless ghosts of the past."

It's a bit of a stretch, but you never know.

Resonance by Chris Dolley which is a Baen book.

2: Not the right book, but it definitely sounds interesting. No vampires, magic, unicorns as far as the blurb implied in the original. :)

3: Yes! And I just mooched a copy. :D