The main recommended reading for this lecture is "Morcos11.pdf". 

Regarding protein-protein interactions, please see "Bitbol16.pdf".

For a general introduction regarding thinking about protein families, please see:
"Bialek_Biophysics.pdf"; chapter 5.1 - Sequence ensembles (p. 304)
This book (Biophysics – Searching for Principles, by William Bialek, Princeton University Press, 2012) is also great regarding other topics!