Say you're a publisher who wants to publish a famous book. Unfortunately, the rights to that book are owned by another publisher, and because it's famous and a money-spinner, there's no chance in hell that they'll let those rights go. What do you do?
If you're Orion, the publishing company that contains Gollancz and Weidenfeld & Nicolson, among other imprints, you have a cunning alternative: snap up the hardcover rights.
For the most part, once a book has gone into paperback, the hardcover rights are virtually worthless. Everyone who was going to buy it at the higher price has already done so. A publisher who nabs the rights and releases the book as a hardcover is going to be competing with a cheaper product, and thus putting themselves at a disadvantage.
Not if you're Gollancz. Their tactic is to release hardcovers of science-fiction classics for the same price as the paperbacks from the other publishers. They manage this by not having a dustjacket (a significant part of a hardcover's production costs), and printing the cover directly onto the book's boards.
Here's their version of the ecological-mystical science-fiction classic
Dune...

..which looks very sturdily appealing next to Hodder's identically-priced and lurid airport-blockbuster equivalent.

And here's the Gollancz version of Philip K Dick's
The Man in the High Castle, one of science-fiction's masterpieces, set in a defeated US divided between the Axis powers.

This competes with the two available attractive but less robust Penguin paperbacks.

(That second Penguin cover doesn't show up well in two-dimensions--it has a sort of Braille-like cover 'image' of the seven continents, now Nazi- and Imperial Japan-dominated, in raised bumps down the right-hand side.)
They're also planning a similar edition of Kurt Vonnegut's
Cat's Cradle, which I'll talk about when a cover design appears.
Having done this for science-fiction, Orion are now turning to "literary fiction" to do the same thing to celebrate Weidenfeld & Nicolson's 60th anniversary. They're grabbing the hardbackrights to books like
Lolita...

..as well as
One Day in the Life of Ivan Denisovich, as well as books to which they already have the rights, like
A Suitable Boy, and the wildly over-rated
The Reader, and repackaging them as a matching set of un-jacketed hardbacks.

(Sorry for the low-quality images--these have been taken from a PDF catalogue, and there are no better versions available yet).
However, this time they're selling the books for about twice the rate of the paperbacks, so I'm not sure how well it will go. Furthermore, I'm not sure that they haven't gone past subtle into the realm of pleasant-but-dull. I'd need to see them in the flesh to see how effective this series design really ends up being.
UPDATE: John Self of Asylum suggests that the W&N Classics will have shapes cut out of the front boards, with the patterns (just) visible above being the endpapers showing through the holes. Now that would definitely make these a more enticing set of books.
UPDATE 2: The ultra-wise
Tulkinghorn points out that the Gollancz
Dune hardback cover is that originally painted by
John Schoenherr for the
Analog magazine serialisation of Herbert's work.