Barrow Keep is tightly scoped, old-school fantasy coming-of-age adventure setting.
It's 72 pages, with two 54 page conversion packs. The packs available are for both the Oldshool Eessentials and Sharp Swords & Sinister Spells engines, and the core book (called Den Of Spies) also feels easy to adapt to just about anything else in the classic tabletop style.
There's no art in the packs, but the art in the core book is lovely and detailed and expressive. It's old-school black and white fantasy art, and it's intensely well executed and adds a lot of character to the setting.
Structurally, Barrow Keep is quite interesting in that it doesn't approach the game world like a sandbox but like notes for a novel. For example, the first thing you do when you crack it open is decide the names and identities of several story-pivotal characters. *Then* you get some information on the titular keep.
If that sounds weird to you, I don't think it's mechanically different from stuff Ravenloft was doing ages ago, but by being the first thing you run into it kind of reminds you to approach this book in a different way.
Barrow Keep isn't Lord Of The Rings. It's the opening acts of Golden Compass and Song Of Ice And Fire, or else it's Gormenghast or Galen Beknighted or Sleepless.
Playing into that, Barrow Keep consists of a number of locations---not physically mapped out, but explained contextually. Each of those locations comes with a list of sensory impressions about that space. You're supposed to play up what these spots look like at peace.
The list of important NPCs the book provides is less detailed, but it's fairly long. There's a lot of faces you can run into, and they all have clear characterizations.
While there are some new items, types of magic, weapons, and other mechanical bits included in the book, its real meat is the keep's secrets. The second half of the book is adventures, hooks, factions, maps, and a whole host of ways for youngsters living in or near the keep to get into trouble.
It's fun and engaging and everything's well written, and I think my biggest hurdle as a reader was simply putting aside my preconceptions that old-school means a bunch of grim 30-year-old freelancers getting shanked by skeletons in an unfamiliar land. Barrow Keep *is* adventurous, and there's plenty of genuine danger, but the tone is warmer and more home-like. This change in tone is its best attribute, and it shines.
Overall, I'd recommend Barrow Keep to new and old groups, to young and old players, and to anyone who likes playing character-focused games that stay put. If you want grim and forbidding, this isn't really that (although you could tweak the tone to be more gothic.) If you want to play a fantasy coming-of-age story where you genuinely like all of the characters, and where the focus is sort of on getting into adventure and learning the scope of the world for the first time, this *is* that, and you should snatch it up.