I have been eating a mainly vegetarian diet for 23 years, every since my then 13 year-old daughter said she wanted to stop eating meat.
Instead of making a special diet for her, our whole family transitioned to a meat-free diet. My favorite cookbook was and still is Laurel's Kitchen. I also use the Moosewood Cookbooks and several Eating Well cookbooks.
It's not that hard to stop eating meat, especially when you learn how to make soups, stews, salads, and casseroles. We usually eat one-dish hot meals in the winter and all kinds of salads in the summer. We have a big garden and I pick my own berries. I strive for as local a diet as possible, especially in summer and fall when local food is plentiful.
From time to time, we eat fish, mainly for heart-health reasons, but we try to get sustainably harvested fish.
I'm glad we changed our diet for three reasons: it's easier on the planet, it's better for your health, and it's less expensive.