Just about every lavish book imaginable was present: an elephant folio of Audobon along with a full set of John Gould's more sumptuous prints of birds; a Kelmscott Chaucer; a page from a Gutenberg Bible; a first edition of Johnson's Dictionary; countless antique atlases of anatomy and cosmography; the Arion Press edition of Ulysses illustrated by Robert Motherwell; hand-illuminated Books of Hours. There were exquisite jeweled bindings, books woven entirely from silk, and doubtless many more things that couldn't be seen in a three-hour tour. The collector mentioned in passing that he was thinking of buying a Wyclif Bible for around $600,000 because he didn't have one yet.
... The collector can afford to let his visitors touch his books. In a way, the books in his collection are functioning as they are intended to function: as objects to be read and appreciated. They're also functioning as signifiers of luxury. His collection is a repository of wealth in a way less metaphorical than we usually talk about library as repositories. No library, private or public, exists entirely outside of this economic system; it's an integral part of the way we consider books.
I would gloss this statement only by deleting "also." The books "function as they were inteded to function, ... as signifiers of luxury." The iconic function of a sumptuous (or rare or old or popular) book conveys status and prestige, to individual collectors but also to institutions, whether libraries, universities or governments.
Visel goes on to describe how university libraries also restrict access and invest in security, and house their books in buildings like fortresses. Making an architectual show of limiting access is a time-honored way of drawing attention to the important treasures inside.