The question of who owns the title of the Earth's cheapest bookstore may soon be answered, with Friday's launch of ClickTheButton.com, Inc.'s free application that enables users to compare book prices of rival online bookstores.

The tool allows users to compare prices at Amazon.com, barnesandnoble.com and Booksamillion.com.

With the click of a corner screen icon, bibliophiles can see prices comparisons displayed in their active browser window. Dubbed The PriceSlicer, the add-on can be downloaded free and works with more than a quarter million book titles on sale at the three book-tailers. The icon is installed on the Windows desktop next to the clock in the lower right hand corner of the screen.

The Princeton, N.J.-based company said it does not have business relationships with the booksellers. It also plans to support additional products and e-commerce sites within the next few weeks.