No, you only need one Bookshelf. You simply tag your cookbooks with a Bookmark that indicates which location the book is in. Many members use this feature to keep track of their cookbook collections in different parts of their house. If you have the same book in two different locations, you can add two different location tags to the same book. Then when you are searching for recipes you filter the results (the Bookmark filters are in the right column under "Only Show") using the location you are at.
More information on Bookmarks.