Book request, can’t remember the title or author

I’m trying to recall the name of this book I picked up in an airport ages ago. I recall something about the author having written The Island though that may be a false memory. Not related to the movie I don’t think. But the main character is this woman who has a glass or compressed needle wound in her arm as a punishment that will never heal, and there is a city surrounded by a desert no one can cross but a plot point is that it WAS crossed by a bioengineered…fleshsuit that protected something that made it past and on to supposedly better lands. There was also an observatory/towering castle in the city and I think a rift down into under city sewer land with monsters?