no matter how long one has been teaching, that mainly helps you understand the concepts really well. the preparation time is still there because you have to make sure the examples you work are correct and you don't get hung up on incorrect details. A conscientious teacher always prepares every night, even a course he has taught many times before. By telling you he is editing several books, your teacher seems to be apologizing for not doing a better job of preparing.
also as you get to know the class you make adjustments in the way you do things so as to be more accessible to the students because of their weaknesses.
At a top school it is easier to prepare in some ways because all you have to do is think about what you are going to do, and you don't have to worry about whether they are strong enough to understand it. you also don't need to do as many exercises.
I also frequently write up complete lecture notes for the class, so the students will have a record of what went on even if they take poor notes. This alone can take 3 hours per class, and that's just for the rough version. I also peruse numerous other books to find good workable problems. I often consult as many as 8-10 books while teaching a class to get the best presentation of every topic.
Of course I don't need to spend much time learning the material, but even there I always try every year to actually learn something new myself that I have never known before, and explain it to the class, to keep it fresh. I.e. I make it a point never to teach the exact same class twice.
E.g. late in my calculus career i realized that archimedes actually would know how to compute the volume of a 4 ball, not just a 3 ball. I.e. he did his calculations based on physical concepts like torque generated by a weight revolving or trying to revolve around a balance beam.
that computation is actually 4 dimensional volume since it multiplies a three dimensional volume of the body by the one dimensional circumference of the revolving beam. Thus since a 3 ball is generated by revolving a half 2-disc around the z axis, so also is 4 ball generated by revolving a half 3-ball around a 4th axis (actually revolving it in 4 space around the plane of the equator of the 3 ball). Since Archimedes knew the volume of a half 3-ball equals the difference of the volumes of a cylinder and an inverted cone, he would have known the same holds for the 4 dimensional volumes they generate under revolution.
Since he also knew the centers of gravity of both a cylinder (in the center) and a cone (3/4 of the way from the vertex), he could have calculated the 4 dimensional volume generated, i.e. the volume of a 4 ball.
thus a 4 ball has volume =
vol gen by revolving cylinder of radius and height R about circle of radius R/2
- vol gen by revolving cone of height and base radius R about circle of radius 3R/4
= (πR^2.R.)(2π.R/2) - (1/3)(πR^2.R)(2π.3R/4)
= π^2R^4 - π^2R^4/2 = π^2.R^4/2.if you want to see the fruit of a few of those hours of preparation, some of the class notes are on my web site. Many hundreds of pages more, on complex analysis, sheaves, riemann surfaces, algebraic surfaces, projective varieties, have never been posted.
I never stole time from my classes to do research, i did the opposite, giving my classes full time, and doing research in the holidays or in time i stole from my own sleep.
That 400 page set of graduate algebra notes took far more than 3 hours per lecture to prepare.That guy you describe sounds like a teacher who doesn't care much or who does not have very high standards for his class. He is just reading the book to you. if that is the kind of teacher you find great, you would probably not like my class. I am a lot more demanding of myself and of the class than that. I would find what he is doing very boring and I think many students would as well.
However I am aware many students just want a clear, unchallenging, explanation of the basic material. And he is giving you that. That is fine if that is what you want. That works for average students who just want to get through the subject and do not really find it exciting, or are just trying to get the basics under their belt for some other purpose.
But even in basic plug and chug classes, I almost never find a book that presents things in a way everyone gets, so i try to expand or vary the presentation from that of the book. After all the student has the book. From me they deserve something more. That's why I am there.
Our staff retypes the class evaluations for us, to maintain anonymity, but so we can learn from them. We never see the originals.