Dinner for 1
I'm staying at the Westin St. Francis for business this week and am looking for somewhere within short walking distance where I can grab dinner alone with my book. ~$25.00 before tax and tip (no alcohol tonight).
Open to any cuisines just wanted somewhere inexpensive, low key, and chow worthy.
Most of those solo-dining threads are about more "fine dining" though. If the weather is decent, some of the places on Belden Place might be nice. Some of the Indian places in the Tandoorloin might fill the bill (since Sultan is gone, I don't know which one(s) to recommend).
44 Belden Pl, San Francisco, CA 94104
Canteen is fantastic for solo dining and low key and casual, but it blows your $25 budget.
Big 4 has a great bar with lounge-y chairs and a bar menu. Big 4 itself is a big upscale but the bar menu (if they still have it) is more relaxed.
On the more budget side, there's Katana-ya. It's low key but it gets packed so you'll get to relax with your food, but not linger when you're done.
There are also a bunch of good indian restaurants a few more blocks away.
54 mint and thermidor are down the hill for you (on mint plaza) and both have bar seating (and if the weather holds, outdoor seating). They both can border on reasonable to more expensive depending on what you order.
I'm sure there are more places -- especially if you want to venture up to north beach -- but i'm trying to think of which ones I'd want to hang out and read in.
The Bar Menu or Happy Hour at Farallon might be of interest to you, even if you're not drinking. Happy Hour at Farallon is one of my favorites for bargain eats in the city.
Agree with the recommendation for Katana-ya, too.
450 Post Street, San Francisco, CA 94102
As said, Canteen would be my pick for a solo dinner but yes it might go a bit over your budget. You can grab a nice spot at the counter and if you loose interest in your book just be entertained by the open kitchen. It also fits your request of "low-key"
Two other places that have not been mentioned yet but might be a bit more noisy are right next door to eachother, Wayfare Tavern and Wexlers.
Perbacco is definitely not low-key but again, a great choice. I have done many solo dinners there. Heck, I do most my dinners solo anywhere where the bill per person is over $10. Lousy friends.