Sending email to professors

<p>I've sent an email a few days ago to several of my professors for the upcoming semester asking for some clarification on the textbooks we need for their classes, but I haven't received a response. Do professors generally respond promptly, or do they take a long time from a loaded inbox/ busy time schedules? Anybody know?
What are your experiences with contacting your profs?</p>

<p>I know I'm an incoming freshman, but I've emailed one of my professors about textbooks a couple weeks ago and she responded promptly for 2 of my emails, but it took her a few days to respond to my 3rd email. It depends on the professor.</p>

<p>I e-mailed 4 of my professors and 3 of them responded promptly.</p>

<p>also realize that some of them may not be available. During the summer is when many professors do major research, so they may be away from computers.</p>