I can think of two interesting ones:

Heinz Knobloch, Michael Richter, Thomas Wenzel:
"Geisterbahnhöfe, Westlinien unter Ostberlin",
Ch. Links Verlag, Berlin, 1999

Available on www.amazon.de.

The title means "Ghost underground stations,
Western lines under East Berlin". The book explores
the fact that some western underground and
metropolitan railways actually ran in tunnels
under the communist part of the city. At the
old stations the trains did not stop, but
slowed to a symbolic halt, making the border
guards visible to attentive passengers. The book
has many beautiful photographs, and a rich and
inspiring prose.

Jürgen Ritter, Peter Joachim Lapp:
"Die Grenze - Ein deutches Bauwerk",
Ch. Links Verlag, Berlin, 1999.

Also available on www.amazon.de

The title means "The border - A German Construction"
(The last past loses some of its impact in my poor
translation, as it is a pun of the wellknown
"Ein deutsches Requiem")

The book deals primarily with the German-German border
along BRD and DDR, which was known as "die Zonengrenze"
(as opposed to the "Sektorengrenzen" within Berlin), but
does mention the Berlin border as well. Lots of good
photos, some in excellent color. A good source for
information on the daily routines of border guards and
inhabitants on both sides of the border. Hilarious
facsimiles of letters from border police officials and
party leaders, reporting on the development of securing
the motherland against imperialistic threat (the border
was known as the "Antiimperialistiche Schutzwalle")
while greeting eachother "mit Sozialistichem Gruss".

In the library
Mats