I recently did a quick review of Brandon Sanderson's Mistborn trilogy. As I've labeled Sanderson among my favorite authors, it shouldn't be a surprise that I thought it was very good.
Alloy of Law is a book set in the same world as the Mistborn trilogy, but three hundred years later, with a changing setting leading to different features of the world. Unlike Mistborn, I can talk about some (though only some) of the things that make this book fantastic without ruining things:
1). Sherlock Holmes expies.
2). Magic gunfighting is awesome.
3). A relatively light-hearted story. (The Mistborn trilogy is a little bit dark.)
The last of these is particularly interesting because in my first reading, I didn't pick up on the callbacks because I hadn't read the Mistborn trilogy just yet.
You can read Alloy of Law without having read any of the previous books; in fact, I think this book stands alone very well for a book that technically is a sequel to a trilogy.
But reading it after knowing what all that stuff is about makes it that much better.
There's only one problem with the book as a standalone or as part of a series: It's clearly part of a larger set of books (it ends on an open-ended but not urgent cliffhanger). But that's not a problem, because I really like the characters and I'd be happy to visit their bit of the setting again.