From her youth, Rachel McMasters Miller Hunt had a strong affinity for plants and gardens as well as for books. These interests eventually led to her developing an internationally renowned collection of botanical books, in addition to manuscripts and artworks. She began early to collect books in her special areas of interest. Her first gardening book, bought at age 15, was Leonard Meager's The English Gardener, or A Sure Guide to Young Planters and Gardeners, London, Printed for P. Parker, 1670.

Rachel also became interested in bookbinding and studied with Euphemia Bakewell, a student of the English master binder, T. J. Cobden-Sanderson. Her considerable mastery of the bookbinder's craft enabled her to produce approximately 90 bindings, many of which are now held by the Hunt Institute. Her binding activity is documented in Marianne Titcombe's The Bookbinding Career of Rachel McMasters Miller Hunt, Pittsburgh, 1974. She also began to collect rare books in earnest. In addition to books on plant-related subjects, she collected works on bookbinding, typography and book production, as well as the products of selected private presses. Much of this non-botanical material resides in the Rare Book and Special Collections department of the Carnegie Mellon University Libraries.

In the Foreword of The Bookbinding Career of Rachel McMasters Miller Hunt, Frederick B. Adams, Jr. writes, "It is rare to find combined in one person both the technical and artistic powers required to carry out satisfactorily all the steps necessary to create a gilt-tooled leather bookbinding from start to finish. For this reason, for several centuries the various stages have commonly been accomplished by different persons in a bindery, sewing by one, forwarding by another, and finishing (tooling and onlaying) by the principal craftsman of the team. But Miss Miller followed through all parts of the process herself except edge gilding, which normally is executed by a specialist possessing the necessary equipment. When the gilt edges of leaves were to be gauffered ... Miss Miller added this ultimate refinement."

"... What inspired her? Quite simply, I am convinced, a passion for books. A visit to the Roycrofters when in her late teens stimulated her to compose, write, decorate, and bind a book of poems. If the verse limped and the lettering lacked polish, no matter-the entire little book was her own creation. In one of her lectures on bookbinding she said: `It adds doubly to the joy of ownership for the bibliophile to have a part in the binding of his books. They should represent his taste and reflect his personality. Few possessions are more intimate than one's books.' She also believed that the binding should be suggestive of the book itself ... or perhaps the mood of the writer."

"When she began to raise her family of sons, Mrs. Hunt realized that she could not do justice both to that task and to her career in bookbinding. So, rather than give less than her best, she completely gave up binding and, deep-dyed bibliophile that she was, turned to developing her great collection of botanical books, prints, and manuscripts."