I don't know when a cookbook has offered so many new ideas as this. I feel as though the supreme test is not in application of the toothsome recipes and provocative menus, but in the reading appeal in mid-February, of a summer cookbook. Hot dishes for healthy balance, cold dishes for hot weather meals, dishes to prepare in advance for weekend hostesses, ideas for picnics, barbecues and those many varieties of outdoor entertainment -- there is wide range here. The recipes are unorthodox, chatty, and while careful as to ingredients and quantities (designed for six), the writer assumes a certain amount of know-how on the part of the cook. One can forgive occasional forays into tricky, woman's magazine ideas, for the general average of imaginative dishes.