I had a lot of difficulty getting good books on the BDG, so this info
may be of interest to someone else who would like a good book on the
gambit.

It took over a year for me to find the book Blackmar-Diemer Gambit
Keybook by Tim Sawyer - THE book to have if you are serious about playng
this gambit. There are reviews of the book on varius sites, but it is
very difficult to find a copy. I ordered it from the Canadian Chess
Federation over a year ago and never received it, and most online
vendors don't have it. A couple of weeks ago it appeared on Amazon, so I
ordered it and received it yesterday - it is new and no defects.

According to Sawyer, the other good book on the BDG is the one by Lane,
so I found that on ebay or Amazon (I don't remember which, since I also
ordered other things) and I ordered that too. Sawyer's book is a
collection of games grouped by variations with a few comments here and
there, and Lane's book goes more into the ideas behind the moves.

Another good source is the CD that contains all the articles from a
magazine on the BDG called the BDG Digest (I think). This can be found
for sale on ebay. There is also a CD by Sawyer that has a collection of
BDG games - maybe the same as in the book?

You can get free collections of BDG games from the University of
Pittsburg web site, but the players are not all of master strength as
they are in Sawyer's book. You can surely find thousands of games on the
mega collections sold by Chessbase and by other vendors, but again the
strength of the players could be variable.

In sum, the best source for the BDG is probably the Keybook, but you may
find it very difficult to find. Used books on amazon sems to be the most
promising place for now.

Having said this, I hope I don't meet anyone who uses this information
on ICC...

Henri