La Guerre Civile is the second book by this now elderly French writer which mentions Louise Brooks. The other is his 1991 novel Un Soir, à Londres, which I blogged about on February 1st.
Though I don't read French, I paged through (aka visually skimmed) the novel on the streetcar on the way home from the library and found the page which includes the reference to the actress. It's page 49. Here it is.