Gilbert Strang's "Introduction to Linear Algebra" made it all click for me. I read it at the beginning of PhD studies and in a few weeks it all made more sense

Gilbert Strang's "Introduction to Linear Algebra" made it all click for me. I read it at the beginning of PhD studies and in a few weeks it all made more sense than during all of my Master's studies before. Coincidentally to this question, he will live stream his final lecture on Monday: https://grinfeld.org/strang/ https://grinfeld.org/strang/ I was amazed reading that, as I wasn't aware he even lectured anymore. And after googling a bit and finding out he is already 88 years old, I was even more amazed. What an amazing human being, probably many thousands of people in the sciences and engineering owe quite a bit to his life's work.