A recent tweet let me to a site for a book-in-progress called Practical Ethnography: A Guide to Doing Ethnography in The Private Sector. It looks interesting. Although it covers some of the same ground as my own book Topsight, it's an ethnographic approach (as opposed to Topsight's case study approach).
The author, Sam Ladner, is a Senior User Researcher at Microsoft and a sociologist by training. And partof what I like about the book description is that you can see her practical bent: the book will cover "How to manage clients and corporate stakeholders while doing ethnography" and "How to get buy-in for ethnographic findings."
The book's site has two sample chapters for download. The writing is engaging, the concepts are well explained. If you're interested in applying ethnography to the private sector, take a look.