Though written in 1934, Louis Shores' Origins of the American College Libraries, 1638-1800 remains the standard foundation for studies of early American college libraries. Shores considers the nine colonial colleges, offering brief outlines of their beginnings and the roots of their library collections. In each case, he examines how the collections came to be accumulated, discovering that the books were almost exclusively the result of donations rather than outright purchases chosen by college administrators.
Shores argues that while having a library was seen as a key element of an institution's reputation, in many cases the nature of the collections was meant that the books themselves were often outdated and "largely useless" (pg. 229). Those few purchases that were made are discussed at length, as is the available evidence for how libraries were administered, housed, catalogued and used during the colonial period.
Much supplemental materials is given here in appendices, including a list of donations to the colonial colleges and information on the various men who are known to have served as librarians.
Near the beginning of his book, Shores notes the irony that "libraries so careful in the preservation of all other materials only too frequently have failed to organize and preserve their own library records" (pg. ix), a fact which makes what he accomplished here all the more important. Yes, there are holes (we know almost nothing about the pre-1800 collections at Rutgers, for example), but Shores has worked wonders with the sources available.
[You'll be seeing many more reviews of books like this as I venture further into thesis-land; my own research focuses on the period immediately following Shores', but of course much of the situation remained the same.]