DETAILS, DETAILS, DETAILS!
When I create the worlds that my players immerse themselves in, my goal is for them to feel that they are a part of a living breathing world. The best way I know to do that is with details, details about everything. So that is what I look for in add-ons or modules.
This book has so many! This is not a book full of generic +1 +2 magic items, or mundane fetch quest hack n slash adventures. The details that have been worked out are so well thought out. You get history, lore, and overall design of the world that has been created.
The items in this book are so well composed, giving you so much to use to intrigue your players. These Relics and Artifacts are so much more than tools, they have character. They come with the description of what it looks like (along with really nice artwork), detailed abilities, lore, it's known current status, and even roleplay hooks that help you insert them into the game. The items alone stand to make amazing adventures for your party, just trying to find and aquire one or two. Even the more standard magic items included are full of lore, like I said, I am all about details.
Also included is a short adventure for your party, which is also much more detailed than most of the modules that I have used. You are given background and history about the area, as well as hooks to get your players headed in the right direction. And the details! Details create immersion, and there are plenty to help you along the way. Details that you wouldn't think about, that after reading it are glad it's there. The surroundings as you are traveling to your destination, stopping points along the way with so many visual descriptives that your players will be on the edge of their seats. Also, the encounter setups are so well done. Such amazing details that make you see what is coming for you so well. And more details, what do characters feel, see, hear, it's all in here! Every area and room is so fully created that you won't have to reach for much to help run this thing. If your players are into story and immersion, there are things in here that will excite them. After reading through this adventure, I have many feelings for the people involved and so too should your players.
In the adventure is also everything you need for encounters too. How you come into contact with things, what they look like, what they are doing, what is around you, even enemy tactics (which is so helpful because, oh yeah, new monsters!). Fully fleshed out new creatures for your party to encounter, complete with stats, abilities, tactics, lore, and even roleplaying tips. (also, several illustrations) With all of the information given, you can certainly run this in theatre of the mind. But, if that's not how your players roll, you have all the maps you need for the entire adventure!
If you are an "expert" or a new DM, I feel that you will thoroughly enjoy this, I know that I have.