Complimenting the author of a textbook In one of my undergraduate courses, I found that one of the required texts was particularly well-written. It is a textbook about computer architecture, and I found that it explained intricate technical concepts in understandable language, and it managed to exemplify and summarize often difficult concepts quite nicely. 

Just so it happens, this textbook was written by someone currently in our Computer Science department (not my professor). Would it be well-received, or at least appropriate, if I sent an email to the author to compliment his textbook? I have no ulterior motive; I'm not trying to win his favor or anything like that, I just simply want to express my gratitude for a resource that was useful to my learning.

(A similar question has already been answered, but I am curious if the answer would still be the same for a textbook.)
I would think you don't even need to go into much detail: just the fact that you have found the author's work sufficiently helpful that you want to express thanks... will be enough, I think.

That is, ... perhaps contrary to the fake myth that textbook and course-notes writers have large, expressive fan clubs... mostly one feels that one is speaking to the void, with no response. (Nowadays even to keep track of IP addresses of hits on one's site seems to require an extra load of various things equivalent to "Google Analytics", which slow things down enormously, so are not usabe... I remember the relatively-better-old days when I could see the IP addresses of people who hit my web pages...)

I myself do make a point of communicating to people whose writing is especially good, at all levels, especially if it's not "heroic, prize-winning" glamor stuff, but is simply very, very good.

We, collectively, should do more of this, I think.