Published in 1936 and still in print, which tells you something on its own.
Most of it reduces to one instruction: stop being interesting and start being interested. Do not criticise, remember names, let the other person talk, make the thing you want sound like their idea. Read cynically it is a manual for manipulation, which is the usual complaint.
I think that complaint misses how much of it is simply attention. Most people are not listened to very carefully at work, and the advantage of actually doing it is embarrassingly large.
The examples have aged badly. The underlying observation has not.
Read December 2023.