@mariannehale You said "...I’m 8 days out, mobility is good (w/ leg and generally) but I just feel bad: disinterested in books, tv, knitting, playing the piano. Not used to being sidelined..."
As a veteran of about a dozen orthopedic surgeries (not knees just yet) I would say you feel "normal for recovery time."

What nobody tells you in advance is that joint replacement is traumatic surgery - in addition to the normal effects of anesthesia and cutting into your body, you have been assaulted. They either cut or moved muscles, tendons and ligament. They cut into bones, and drilled, hammered or glued to put in new pieces. They inserted foreign material. Then they stapled you back together and sent you home to recover.

Just recovering from all of that takes 6 weeks to 3 months for most people, then the rehab with PT and having everything knit together can take up to a year.

So at 1-6 weeks, just making it through the basics of eating and sleeping, with a little stretching thrown in, is all you can do. Gradually, as you heal, you'll be ready to pick up favorite activities. All of a sudden, after a few months, you'll realize your energy is back.

Hang in there. Rest & heal. Come back and chat if you want to know whether what you are feeling is normal (for now.)