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.)