Hilbert Bernays Grundlagen der Mathematik appeared in two volumes in 1934 and 1939, a second edition in 1968 and 1970, all published by Springer. It is the foundation of proof theory, a major source on David Hilbert's programme and Paul Bernays' philosophy, the epsilon operator, and much more.
It has influenced mathematics, logic, and philosophy like no other book in the 20th century apart from the Principia Mathematica of Russell and Whitehead. The presentation is excellent and reading of it is fun. For us, it is one of the most fascinating books ever written.
Today, however, the German original is out-of-print and available as an expensive collector's item only. Moreover, English has become the language of science, but the book was never published in an English translation. We are changing this by publishing our bilingual German-English edition.