If the library and the books in it were used, yes - it could be a reflection of Gatsby's varied interests and education. Unfortunately, however, the library - as with much of the rest of Gatsby's mansion - is intended for show, to impress others, rather than for actual use for gaining knowledge.
The man inspecting the library shows Jordan and Nick a random book, Stoddard Lectures, Volume One. He is surprised and impressed to realize that it is an actual book.
"See!" he cried triumphantly. "It's a bona-fide piece of printed matter. It fooled me...What realism! Knew when to stop, too-didn't cut the pages."
The book is brand new and has never been read. The pages were printed and bound into the book's cover on folded sheets of paper, several pages on each sheet. In order for the book to be made readable, the folded edges of the paper would need to be cut or slit to create separate, individual pages in the book.