The over 60,000 volumes constitute the "world's largest open-shelf collection of science fiction"; although the Eaton collection of the University of California, Riverside is larger, that collection is not on open shelves. According to MITSFS, the library once included "over 90% of all science fiction ever published in English", although a profusion of self-publishing now may have outdistanced it. The library is freely available for browsing by the public, as well as for borrowing by members. Membership is open to anyone who pays the modest dues and agrees to abide by the rules.