One of the book I would recommend is "The Art of Managing Professional Services" by Maureen Broderick. There are dedicated sections on KM in there, including some stories about Grant Thornton. While it is from 2010, I still that that the main points advanced by the author about both Professional Services and KM in Professional Services are true.
Our company is 100% focused on KM in Architecture and Engineering firms. While the terminology and business is different, I think there is enough similarity between Professional Services that you might enjoy the content on our site. We have a talk archive from our annual KM conference, a book list, and a periodic table of common KM program elements for Architecture, Engineering, and Construction (AEC) that breaks down the way we look at KM our the industry. I have attached the periodic table. You can watch a short talk explaining it here.
I hope that helps.