I took a linear algebra class in high school and we used two textbooks for the class. One gave a simple and soft presentation which we used most of the time. The other one was much more rigorous, referred to in hushed and fearful tones simply as "Strang". When I got to university, I realized with fear and excitement that the guy teaching the linear algebra class is the same guy who wrote the textbook we were all afraid of in high school. His lectures are excellent. Just as clear and rigorous as the book, but not at all scary. Just like Strang himself.