I haven't read The Credible Company yet, but that shouldn't stop you from reading it, especially if you've never read Roger D'Aprix before.
Reading D'Aprix is realizing for the first time that you really haven't known what you were doing in employee communication all these years while simultaneously thinking, "I've known all this all my life."
D'Aprix's at-once bracing and comforting combination of business realism and basic humanism will make you understand your work in the rich psychological, social and political context in which it rightly and properly belongs.
Just reading D'Aprix can transform you from a clever tactitian into a complete communication philosopher. (Even if you think you're a complete communication philosopher already.)
Have a read, and let me know. (I'll have read the book by then myself.)