The Folio Society is a publisher of quasi-fine hardback editions of books, previously sold only by catalogue and subscription, more recently online and in bookshops. The Society was founded in 1947 and publishes on the occasion of each decaversary a celebratory anthology, identifiable by the title »Folio [#0]«. The company is based in the United Kingdom and tends to work with British printers, which is rare these days.
Although the concept of the Society was to produce fine bindings, their regular editions are cloth-bound at best; this is somewhat hypocritical but also very understandable, considering the present and historical expense of leather binding; nevertheless it is in some sense an instance of false marketing. To their credit, the Society does also produce some limited editions, which are legitimately good, and sadly, priced accordingly. Particularly worth remarking on in this regard is their Letterpress Shakespeare, a series of the works of William Shakespeare which are printed with lead types on an old-fashioned letterpress. These are actually not limited, as the market for them is apparently sturdy enough for the Society to keep them in print on a rotating schedule at least, which warms a stodgy weirdo's heart. They are extremely, extremely nice, especially by modern standards.
Entirely aside from these limited editions, Folio Society books are quite, quite expensive as it is; you will rarely pay less than $50 for one book. As such, they make excellent presents for any bookish people you might know, not that anyone here would have any friends, family or vague acquaintances like that.
The paper in Folio Society books is decent, the bindings sturdy, and the typography frequently very good; unfortunately, they often fall through on the illustrations and cover design. These latter have essentially the same flaw, which is that they try to be modern in a prestigious type of way; this means the illustrations are frequently some inscrutable scribbly shit, and what's worse, the covers sometimes look like an explosion in the camp factory. Whenever they have the good sense to be traditional, or even just tone their »avant-garde« shit down, the results are usually good, though.
They used to offer a subscription service, whereby the subscriber would pledge to buy a certain number of books (four, I think) in one year and would get a good deal on some package of books (commonly the popular Folio editions of Lang's Color Fairy Books) in return, but have apparently revamped their model in the last year or so and just sell over the internet, as well as offering an assortment generally to bookshops for the first time. (It's possible that they still offer memberships, but if so it is no longer anywhere visible on their websites.) Prior to this it was already possible to find Folio books in museums and the like, indubitably a vector of discovery the Society would not gladly have done without. Used bookshops have always done and continue to do a brisk trade in old Folio volumes, not least because they stand the teeth of time reasonably well (but don't get me started on the degenerate nature of pulp paper).
The interested may peruse their catalogue here.