TL;DR: It's great. Buy it. Use it. Your players will love you.
The idea of my players having a castle has always been present in my mind, and I've been DMing for 15+ years. Once (back in 3ed I think) I even bought a splatbook for stronghold creations, but it was just too much work - I didn't want to build every single room, plan out every single floor and wall. Bleh. Too much work - RPGs are only one of my hobbies and I also have to work and have a family.
Resources on the Internet are also too complicated and time-cosuming (and not easy to find!).
Then there is this short book - yes, it's concise but that's great - the author gets his point directly across, without unnecessary (for this type of book) embelishments. So, first of all there are the ideas how to insert this Sleeping Manor (love the windows!) into your campaign. Make sense. Then there are descriptions - very nice ones, and each room is presented in two versions (lavish and utilitarian), so the players can choose what they like. THERE ARE NO FLOOR PLANS. And GOOD! I'm from the faction that believes that the moment you show a map to the players, their imagination turns off. There is also a simple and fun system for earning money between adventures.
Next - a number of upgrades for the house. This is the part your players will really love. For example, having a peaceful garden allows the heroes to start their next adventure with extra HP, having a wizard's tower allows the wizard to prepare one more spell, an alchemical lab (witha resident gnome) produces low-level potions and much much more. So the players now want to come back home - because resting there grants all these small, but useful bonuses!
The other part of the book describes neighbours and lands around the Manor. Plenty of great roleplaying opportunities and I estimate that visiting each location can be enhanced and become a separate game session. The ideas are ineresting and leave enough space for your own plot hooks etc.
Finally, there is the Baron - an adversary, whose lands border the PCs' lands. Again the book offers only the spine of what could be a really great campaign, it is solid and inspiring. I really, really dig the idea of my players leading a fight against their neighbour, supporting the rebels on his lands, learning the secret of his power, protecting their home, lands and people! FUN!
The book looks nice, although nothing really stands out - the images look like standard stock photos (they probably are heh) or they're from the monster manual. There is a hand-drawn map at the end, but I've seen better.
To sum up - a really great, small book! It might seem pricey compared to other DMG products, but trust me - it's worth it. I love it so much I might buy it again :D
[5 of 5 Stars!]