From the text of the law:

"(2) No reproduction, distribution, display, or performance is authorized under this subsection if— (A) the work is subject to normal commercial exploitation; (B) a copy or phonorecord of the work can be obtained at a reasonable price"

I'd imagine that "normal commercial exploitation" would generally mean an item that is currently in print, although I could see other theoretical cases this would cover (for example, the work is not technically being printed anymore but there is a huge stock of existing volumes on the market).

I don't think reselling rare volumes would fall under this category - that could be "commercial exploitation", but certainly not "normal".