Original 1941 Schlag nach! Wissenswerte tatsachen aus alle gebieten. Thick, well used but still nice book which contains a little bit of everything. It can't make you a master of any one subject, but it does give you enough information about almost anything to get by. This is probably the sort of book I would have in my tornister. There are a few missing pages, which look a bit like the glue holding them in just gave up (or perhaps they were more political and were neatly edited out after the war).
