I saw a link posted to a rather short note on graphs and linear algebra. I thought I'd better do some advertising for the real deal!

Took Spielman's spectral graph theory class back in the day. Was really cool to see the professor engage with students on open questions that pushed at the boundaries of research!

This is also an excellent book on the subject: https://bookstore.ams.org/cbms-92

This link doesn't work. Maybe just give the name of the book, and author?

Edit: I guess the link DOES work, it's just overloaded ...

Spectral Graph Theory

Fan R. K. Chung, University of Pennsylvania