This is wonderful compilation of mechanically beneficial background secrets and story starters. I will definitely be using this for all future campaigns, and makes me want to start a new one ASAP! There is definitely something for everyone here, as not all of the secrets are Eberron specific. I think this is a great way to make the player characters stand out even more amongst others, and it gives players permission to play larger than life characters with deep and interesting backstories. The art and editing are fantastic, and in total really fits well into the Eberron aesthetic.
My only complaint is that there are a lot of very Eberron specific secrets that need a bit of finagling to make fit into other settings so YMMV. The good news is that they provide a blank template to make your own. AND they go well into depth about every secret which provides good clues on how to make it work in a campaign outside of Eberron as well.
Definitely worthwhile to any DM that wants to make character creation a little more fun and play with story-rich backstory.