Are there any books that specifically focus on how to profit in a
declining real estate market?

I have found this resource for you on Amazon.  It may be what you are
looking for and the reviews look good.

Author: John Rubino, How to Profit from the Coming Real Estate Bust :
Money-Making Strategies for the End of the Housing Bubble (Hardcover).

Link:
http://www.amazon.com/gp/product/1579548709/102-9038519-5535363?v=glance&n=283155

I had a RE license up in MA (now in FL).  Getting a RE sales license
is a very cheap way to get and education about RE.  It costs about
$200-300 for the course from most states and the test is usually under
$100.  It can be done in a week, on weekends, nights and fits your
schedule.  You don't actually have to USE the RE license (or even
register to take the test) to use the knowledge from it.  Just an
option for you.

BTW, I messed up on the first comment, the little pinky finger hit
RETURN a tad too quickly.