I was in a Borders Express last weekend and I found a copy of  the re-released Cotillion, by Sourcebooks.  What made it unusual was the fact it wasn't the trade paperback I had seen at the B&N and online.  It had a different cover, ISBN, and it was a regular/mass market paperback.

Is this something usual for Sourcebooks, to release both concurrently?  I prefer the mass market size personally and hope that I get as lucky with An Infamous Army. :-)

I've tried looking up the ISBN without any luck, even on Sourcebooks website.  They don't have it listed, just the  TPB.