Recent scholarship has studied Hellenistic libraries at a more granular level, by distinguishing the institutional libraries of the 2nd century from the less formally constituted book collections of the 3rd century, and by casting doubt on much of the unreliable, anachronistic late literary evidence that romanticizes the Library of Alexandria (e.g. Galen, Athenaeus). For example, Johnstone 2014 and Hendrickson 2014 cast doubt on whether the Library of Alexandria really existed as such in the 3rd century, and I write about this issue extensively in my dissertation. Clearly the early Alexandrians had a large collection of books at their disposal, but these books do not seem to have been a very important part of early Ptolemaic cultural policy, whereas the Museum clearly was. In this section on "Virtual Libraries" it might be worth defending the historicity of sources such as Vitruvius and Galen if you think they are reliable, and clarifying which period of Ptolemaic rule is under discussion.
– Hendrickson, T. 2014. “The Invention of the Greek Library.” TAPA 114: 371–413.
– Johnstone, S. 2014. "A New History of Libraries and Books in the Hellenistic Period.” Classical Antiquity 33: 347–393.