change in file crepbook.cls line 230
@ -227,7 +227,7 @@
% Customization of the page appearance
%
\RequirePackage[
a5paper % paper size
a4paper % paper size
,includeheadfoot % include header and footer into text size
,hmarginratio=1:1 % ratio between inner and outer margin (default)
,outer=0.5cm % outer margin (right)