Sisters of Berlin by Juliet Conlin is a good story, especially if you know Berlin - a bit of Wall and a modern day mystery
The Moment by Douglas Kennedy is set E and W Berlin, emotive and gripping
1989 The Berlin Wall by Peter Millar, always a good writer
Agents of The State by Mike Nicol
Go Went Gone by Jenny Erpenbeck is very Berlin reflecting on now and back
The Standardization of Demoralization Prodecures by Jennifer Hofmann (I couldn't get on with this one at all, but it's very much about the Wall)
Learning German (badly) by Tim Luscombe, memoir set in Berlin - a Brit's perspective on life and history in the city
Well, you have probably got enough to be going on with... enjoy your 'trip' to Berlin