What is a good cookbook for cold dishes?

I've really enjoyed the dishes out of Veganomicon (I'm not even vegan). Other good ones are Jerusalem by Ottolenghi and anything by Heidi Swanson.

I don't have specific recommendations, but Italian appetizers/antipasti would serve this purpose; mezze dishes would also be suitable. Deborah Madison's classic Vegetarian Cooking for Everyone has an extensive salad chapter, as do all the Moosewood cookbooks (they probably have just a salad one by now). Also look for "entertaining" cookbooks that focus on simple dishes made for parties where food isn't going to be served hot. Get really good at making roasted vegetable salads (beets and carrots with a cumin-y dressing is great); they are great cold or at "room" (in your case, roof) temperature.

You could make many of the above types dishes when you have time, in large quantities, and they'd provide several days' worth of variety at the table. If people are choosing from a "spread" of dishes versus one course, they won't mind encores. Adding bread or grains or a pasta salad, make sure you have some protein (beans, hummus, nuts or animal-based) and nobody will notice that you've been using the same dishes each day.