There is a two volume bound set of the History of Zeta Tau Alpha out there, as well as some staple-bound addendums with history updates for the timeline past the bound edition. Supposedly IO has been working on republishing the volumes, but it's been a few years since that announcement.
http://www.biblio.com/books/50390049.html
http://www.biblio.com/books/123803160.html
http://www.biblio.com/books/130872913.html