The prime reason this likely exists is for United to give as gifts (ie, "swag") to people.

The way many companies marketing departments operate now days is that use they companies like Summit Marketing (the company who's website you're actually going to when you buy this book) to handle their internal marketing swag stock. If you work for United (eg, in sales, marketing, etc) and you want to send your customers or prospects a christmas present, you go to this website and order 20 cookbooks, and then give them out to your customers. Want to give out some United notebooks or playing cards at an industry event or conference? Same thing.

Most of these marketing companies then have the ability to make some (but normally not all) of the items available for purchase by the public as well, often at a higher price, and that's obviously what they have done here.

As odd as buying a Polaris Cookbook might seem, getting one from United as a thank you gift for something does actually make sense.