Kasparov/Nikitin book still worth having.  Verbal explanations and some of the analysis still topical, some areas obviously out of date.  Use with caution.   

Pedersen was a useful summary in its time, but now dated.  Not worth getting.

Emms is excellent, but only from Najdorf move order.  No coverage of the Modern Scheveningen (w/o ..a6) or Keres.

A handful of pages on the Modern Scheveningen in Revolution in the 70s.  Not worth getting on that basis alone, but you should get the book anyway.

 

I have Pritchett's book which I find OKish. I do get the impression that it is two books in one: a very detailed look at mainline scheveningen with Be2 where black doesn't play a6 quickly and a repertoire approach for everything else. 
I also have Adjorans "Black is OK... forever" (long live the bargain bin) which I find a very interesting book. A lot of Keres material in that book and some strange but wonderfull essays about a lot of topics. 

I'm in Louisiana and unfortunately competitive chess seems pretty dead here.  A player rated under 2000 USCF just won the state championship.  I think Mississippi might be even worse off.  I could go to Mobile, AL to play in some tournaments sometime maybe.  I play on FICS in the Teamleague.  I'm rated around 2000 on FICS but I think I'm underrated by about 100-150 points or so.  I haven't played in a while but I plan to play in the next Teamleague tournament in January and I'm hoping that my rating will go up some more.

Another source that would be great for you would be the Bookup ebook on the Scheveningen.  Black is OK! by Adorjan has some Keres analysis not covered in the Starting Out book.  I think Pritchett may have given the wrong book title in his Keres annotatations unless the sequel to this book has updated Keres analysis.

I haven't had much use for the very old Kasparov book.  I think it's probably too outdated.  There are two German language books from something like 1998.  I don't know how they are or what lines are covered.  I saw them on Ebay recently.  If you can read German these are probably worth getting.

The Emms book is great.  There are some lines that will transpose or offer you nice alternatives to Pritchett.

Experts vs the Sicilian has a lot of Keres material from the White side.  It's probably the best source for a lot of the Keres lines.

If you come on FICS we can look at it.  I'm working on the Scheveningen off and on also and I've been looking at it with another person on there.  Maybe we could even do some team games for practice.

Black is Still OK by Andras Adorjan