The tools build on the vast amount of information Google knows about consumers.
The booksellers today began doling out credits as part of an antitrust case settlement against several publishers.
Amazon.com Inc. and Barnes & Noble Inc. have sent consumers who bought its e-books between April 1, 2010, and May 21, 2012, an e-mail alerting them that they have received a credit as part of a settlement between some of the largest U.S. book publishers and a coalition of state attorneys general.
The states claimed that five publishers—Hachette Book Group Inc., HarperCollins Publishers Inc., Simon & Schuster Inc., Macmillan Publishers Ltd. and Penguin Group USA LLC—and Apple Inc. colluded to artificially inflate e-book prices.
Amazon customers can apply the credit to either Kindle e-books or a print books sold by Amazon.com. Similarly, Barnes & Noble customers can apply the credit to the retailer's e-books or print books.
Amazon is No. 1 in the Top 500 Guide and Barnes & Noble is No. 27.