Is that a good idea to send an errata list to a professor whose class I'm currently enrolled in? There is a professor at our school whose textbook I was using in class A (not taught by the professor). I've studied the textbook from cover to cover and have spotted about twenty typos (many of which are quite serious, e.g. make an exercise unsolvable). I wanted to TeX them into a list and send it to the professor yet the following two aspects concern me:


I'm currently enrolled in his class B (not the book's subject). It's a rather small class and he knows me by name. Wouldn't it look as if I'm trying to improve my standing in his class by submitting the list?
It's known to me that the professor is aware about some typos (since he commented on a couple of them while teaching from the book two years ago). Yet for some puzzling reason there is no errata list on his website. It gives me an impression that he might be somewhat unhappy to see the extended list of typos. 


The professor is working in the field I'm interested in, so I'd definitely like to make a good impression (and more importantly not to make a bad one). So is there a way that sending the list could harm me?
Unless the professor is a total jerk, I don't see any way this could hurt.  My experience has been that academics in general are quite happy to hear from people who are interested enough in their work to offer corrections.  (This has been the case even with authors who, for whatever reason, don't post errata.)

I wouldn't worry about being seen as kissing up.  But if you are concerned you could always wait to send it until after the end of the term.

Before sending it, you may want to casually mention: "I've been reading your book which I really like.  I did notice a few typos though.  Is there an errata list posted somewhere?  If not, I could make a list of the ones I found and send them to you."

If there is any chance that a given typo is not really an error, but something you have misunderstood, you can be more delicate by phrasing it as a question.  Instead of "On page 34 you forgot to require that X is compact" you could say "Are you sure the argument on page 34 works without assuming that X is compact?  Isn't the punctured plane a counterexample?"