Dear Professor Schorsch,
I do not own a copy of the book but I found it at the SS. Cyril and Methodius National Library of Bulgaria. Here is the link to the book you are looking for: http://www.theeuropeanlibrary.org/tel4/record/3000047181945?query=Еврейският+въпрос+и+социалната+демокрация
The book's national bibliography number-NBN is "БКГ1878-1944 - 2612."
I hope this helps a bit.