Encrypted is set in the same world as Lindsay Buroker's Emperor's Edge series but takes place slightly earlier and only has one overlapping character. It is a complete story that stands on its own just fine and doesn't require any of the other books to support or inform it. It has all the witty charm and almost over the top adventure of the Emeror's Edge books but more romance and a broader political landscape.
If you've read any of the Emperors Edge books, Encrypted adds some interesting background to the mysterious assassin, Sicarius, and another dimension to the world.
If you haven't read the Emperor's Edge books then you're in for a treat because you'll definately want more after reading Encrypted. Lindsay Buroker's stories are like chips... bet you can't read just one.