The books are not correct as far as practice goes. 10% was standard for years and 15% for great service. Waiters of course have been trying to promote 20%, 22.5% and more as normal.
10% is not great, but is what senior citizens and rich politicians will leave if they tip at all.
10% is considered an insult in California, and will be treated as such.
I accidentally left a 10% tip at Fisherman's Wharf (Early on in my california experience), and was approached by the Maitre D as I was departing, asking what was wrong.
If you can't afford to tip, best just not to eat there in the first place.
I've also noticed that many lower-end restaurants will print pre-computed tip values at the bottom of the sales receipt for 15%, 18%, and 20% (both as a prompt and as a "nice" thing to do so you don't have to do the math yourself). But these values seem to always be calculated off the post-tax cost of the meal, whereas convention seems to be that you tip based on the pre-tax subtotal.
10% is not great, but is what senior citizens and rich politicians will leave if they tip at all.