To expand your search beyond the Five Colleges, try
National Library of Medicine (NLM) Locator Plus
A catalog of books and other material.
A worldwide catalog.
These collections provide the capability of searching the full-text of all books, whereas the 5-College Catalog does not.
Springer E-books 1815+
More than 250,000 books published by Springer and its subsidiary imprints, covering every scientific discipline and some coverage of the social sciences & humanities. Includes access to Springer's Print on Demand Service (MyCopy)
Proquest E-Book Central
A very large collection of Ebooks, mostly scholarly, spanning the humanities, social sciences, and sciences.
National Academies Press
Over 5,000 books on a variety topics in science, technology, and other disciplines. Books are free to download.
A significant selection of full-text books available from the National Library of Medicine.
Growing collection of books, some with complete full text online, others with only a small portion. Limited printing and downloading.
EBSCOhost eBook Collection
Full-text e-books on a broad range of reference, scholarly and professional topics. Includes books formerly in netLibrary.