Then I went to Amazon itself, and discovered that my email and password indeed had been changed - and I was locked out of my account. I log onto Amazon only from my home and work PCs, and my password isn't easy to guess, so I have no idea how this could have happened. Maybe someone was using a password-generating program and managed to get in.
After spending about 15 minutes on the phone with a customer service rep from India, verifying various address/credit card details, I have my account back. I'm just fortunate I had the PC on when that password-change email came through, or else someone could've gotten in and bought whatever, using my credit card, and had it shipped to them.
Anyhow, if you get an email regarding a password change from Amazon, don't assume it's a spoof - check the message header to be sure.
Book pile photos coming up.