Hopefully in a not to distant future (this year) there will be a new book about the Ju 52 by Lennart Andresson, Günther Endres and Rob Mulders
http://www.eambooks.com/AircraftJu52.html
I've heard that it at the moment weigh in at 2 kg... :-) so if you're just going for one Ju 52 book I think you might consider waiting!