How strict are you going w/vegetarianism? Eating eggs? Dairy? Fish? It does make a difference in terms of how full you tend to feel/how readily you get your nutrients in.
The Moosewood Cookbook is traditionally a very, very fatty cookbook. Personally I don't recommend it. It's vegetarian but it is cheese and butter city. I just looked at it on Amazon and it is better than I remember it but do be careful.
Moosewood Cookbook. I think you'd do better looking for a low fat cookbook and adapting it for vegetarian, rather than vegetarian and adapting it for low fat, if that makes any sense. Of course fat isn't the only source of calories but if you go for a low fat book it will, by definition, not have a lot of meat-heavy recipes in it.
This one happens to be both low fat and veg and is well-rated by Amazon. I have not read it but Amazon is a good source. I'd do what I did (of course!), e. g. do a search on low fat or low calorie or vegetarian cooking and have the results sorted by average customer review. That should give you an idea of whether the recipes are easy and tasty.
I was a veg (no red meat, no poultry; now I eat poultry) for 15 years, from 13 - 28 years of age. The restaurant issue, of having few options and having them crystallize your thoughts, is exactly what my experience was. It is again, these days, as I don't eat red meat and of course I'm watching. So I have fewer choices, but I tend to find that liberating and easier.
Enjoy -- in Philly, we'll grab something veg. My friend won't mind; she more or less eats that way, too.