How about "The Universe and Dr. Einstein" by Lincoln Barnett with a forward by Dr. Einstein himself? Serious enough for you? In Chapter 6, using the train-and-lightening thought experiment, he claims that the observer riding at the midpoint of the train will see the forward strike before seeing the rear strike. Not so. Since the train is an inertial reference frame it can be considered "at rest" while the countryside rushes past. SR says that the measured speed of light is the same for all observers. This includes the observer on the train. It is the trackside observer who sees the front strike reaching the train observer first, not the train observer himself. This isn't the example of the error I originally posed, but it is another false conclusion from a "serious" source.