I have posted before that I think it is very important in teaching to present students with comparisons of theory with actual experimental data. It is disturbing that many teachers and textbook writers make little effort to do this. On a positive note, here is a particularly nice comparison.
In PHYS4030 Condensed Matter Physics this week I am teaching Paramagnetism and diamagnetism, closely following chapter 31 of Ashcroft and Mermin.
Consider non-interacting paramagnetic ions with total angular momentum J in a magnetic field B at thermal equilibrium at temperature T. Basic statistical mechanics can be used to derive an expression for the magnetisation, which is a universal function of B/T, known as the Brilloiun function. A&M do not compare this to experiment. However, I recalled that when I was an undergraduate we used a very nice book, Heat and Thermodynamics, [5th edition] by Mark Zemansky. It contains the comparison below, taken from a 1952 paper by Henry.