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Adding tables to your query grid isn't much use unless you can use the fields in those tables, right? Access lets you add fields to your query once you've selected the tables you want.
You should add any fields you want to appear in your results or any fields that will help you find the records you want. If you want to find every book by a certain author, for instance, add the book's author and title. Adding the publisher and copyright year is probably a good idea as well.