Good morning Bonnie (and it is a beautiful morning in our part of the world)
You can currently search for recipes by individual book titles. Just enter "The Best Quick Breads" (including the speech marks) in the search terms box. Thern use Only Show filters on the right and select pumpkin by clicking Ingredients, Vegetables, Pumpkins & squashes, Pumpkin. You will then just see all the recipes in that book that contain pumpkin. Alternatively, you can enter pumpkin in the search terms box after the book title, which would give you the same results in this case.
In general though, you get more precise results by using the Only Show filters. The search terms box looks for the word you enter in recipe name, ingredients, author name, book title, e.g. if you enter chicken in the search terms box you also get chicken stock, chicken of the woods mushrooms, chicken bones, recipes in books with Chicken in the title, etc. The first selections will always be where the term appear in the recipe name. But if you select a type of chicken in Only Show filters under Ingredients, Meat, poultry & game, Chicken then only that ingredient will appear.