The XPS (XML Paper Specification) file format is Microsoft's alternative to PDF. Files of this type include fixed layouts and can contain digital signatures, images, text content, and many others. Unfortunately, OS X doesn't provide you with a default reader for this format. For this reason, apps like XPSView were developed.
This program enables you to open and read XPS and OpenXPS files, print them directly from its interface, and copy their text content to Clipboard. You can also use this app to manage the bookmarks of the input files.
What's more, you can use this utility to extract the contents of your XPS files and save them as individual images or text documents.
Other than that, not much more can be said about XPSView. It simply does what's being stated on the homepage of the developer.
In conclusion, it's worth buying this application for your Mac if you need to open and read the contents of a XPS file. The program provides you with plenty of useful features, is very simple to handle, and comes with an adequate cost.