Several options are available. 

• Your best bet is to use the Library Catalog.  After you do your keyword, title, subject, etc. search, you may limit your findings to (1) Full text Online, and (2) Source Type: Books.

• You may also separately search the ebook collections below.
  • eBook Central 
  • eBooks in EBSCOhost 
  • MAS Ultra Reference eBook Collection
  • Middle Search Reference eBook Collection 
  • Oxford Scholarship Online 
  • SAGE Knowledge
  • Salem Press eBooks 

• You may also search Databases A-Z: Books and eBooks.  Note that many of these sources list articles and other publications, in addition to ebooks.