It is amazing but I never took an introductory Solid State Physics course, either as an undergraduate or as a graduate student! As an undergraduate at ANU, the course was an elective and so I avoided the course because my previous experience with the lecturer was he was incompetent. At Princeton I had to pass a "General exam" which covered solid state, nuclear, particle physics, and general relativity. I taught myself solid state physics by reading a library copy of Ziman's Principles of the Theory of Solids. I don't remember why I made this choice but I suspect it was partly that Solid State Physics by Ashcroft and Mermin seemed too big.
I think the approach of Ashcroft and Mermin has incredible value because it shows how good science is done: looking at experimental data and then developing the simplest possible model to explain the data, and using data to eliminate competing models. This is a great example of the method of multiple alternative hypotheses.
I also think reading the first few chapters helped me to do some of my best research. It helped me appreciate the different signatures of a Fermi liquid with coherent quasi-particles compared to a "bad metal" with incoherent excitations. These ideas were key in writing a paper Transport properties of strongly correlated metals: a dynamical mean-field approach with Jaime Merino.