Hollow World is one of the first reprint-on-demand books available at Wizards of the Coast's dmsguild.com site, and also the first one I ordered to check out the quality of the print. The book arrived today, and here's the lowdown:
What is it?
If you're wondering what Hollow World even is, it's a sourcebook for a literal hollow planet in a D&D setting called Mystara, although the book provides guidance on placing it at the heart of any fantasy realm if you so desire. The setting is one of D&D's more unique visions: a domain of lost kingdoms and fallen empires, a population of each sequestered away inside the hollow planet, with a strange day/night process, in which ancient Immortals have decided they will keep a record of these fallen empires. The many empires of the Hollow World are based on analogs of ancient civilizations of Earth, and in their default setting represent a who's who of the ancient history of the B/X universe of Mystara.
My suggestion is to grab the Duchy of Karameikos from the Gazetteer series to establish a "locale" for PCs to be familiar with on the surface world, then let them stumble upon a means of reaching the Hollow World from there (the core book includes scenarios for just that purpose).
Hollw World contains a lot of useful information for a B/X or BECMI era D&D game, but you could easily convert this to D&D 5E with minimal fuss, mostly through substitution (i.e. use the appropriate D&D 5E monster stat in place of the one in the book). It would also run just fine with current OSR systems like Labyrinth Lord, White Box or Swords & Wizardry Complete with almost zero fuss.
In the original release it was a boxed set with three books and a fold-out map set. The new print on demand edition is a single soft-cover volume with a full color interior on nice quality paper...the description on the product page says its standard heavyweight, but not premium...but it looks pretty damned good.
The resolution/quality is pretty much perfect. This does not look like a print from a scanned copy....it looks as good as any current release. It's got a tiny bit of that POD-level graininess (mainly to color illustrations) you might be familiar with, but I had to really stare at it a while to notice. The readability of this is A+ though. Only exceptions I can note are a couple regional maps in the Player's Section are too dark for my tastes.
The core three books of the original boxed set are bound in one volume. In the back are eight full color pages of the Hollow World maps. It's a very usable format. You will want to either grab the old BECMI rulebooks to run this baby, Labyrinth Lord (or similar) or pull out D&D 5E and start converting (my plan).
(UPDATE!) Some Pics:
I have many more of these new reprint-on-demand editions on the way. Hollow World has bolstered my confidence in the anticipated quality!