Eberron is one of the most interesting of the D&D campaign settings. Most fantasy worlds are stalled in a permanent Middle Ages. Eberron is a world that has had a magical industrial revolution. There are magic powered trains and airships. There are big cities with universities, newspapers, hotels and restaurants. The tone is post-WWI Europe meets steampunk, which is a bit unique as steampunk tends to be a bit more Victorian.
As a campaign setting Eberron is very rich in mysteries and potential threats. The authors are going for a Noir feel with lots of criminal organizations and political conspiracies, but retaining the traditional D&D elements such as mad cults and demonic incursions from other dimensions. There is even a slightly woke touch to Eberron in that Orcs and Goblins are not automatically assumed to be evil and Elves and Halflings are not assumed to be good. Overall, a useful supplement if you are looking to launch a new campaign in a fairly unique setting.