How about changing to this logo?
It better resembling three main wikimedia's color scheme end also resembling many different types of book
CC BY-SA 3.0 license
The WMF legal team has started changing the copyright status for the Wikibooks logo. I would really appreciate your help if you would like to replace the copyright template with the CC BY-SA 3.0 template on the different language versions of the Wikibooks logo. But please don't change the copyright status on any of the other Wikimedia logos for now. We're still working on those. Thanks, YWelinder (WMF) (talk) 20:10, 19 March 2014 (UTC)