(CNN) -

Rep. Paul Ryan's first solo book sold 6,266 copies in its first week of publication, according to Nielsen Bookscan data provided to CNN by a publisher.

The number puts Ryan's "The Way Forward" behind two other books by conservative authors, "America" by Dinesh D'Souza and "One Nation" by Ben Carson, both of which have been out longer than "The Way Forward," according Jason Pinter, the founder and publisher of Polis Books.

The Nielsen data makes up roughly 85 percent of all retail book sales but does not include e-book and preorders.

"Considering two years ago Ryan was the VP nominee and a rising star, first week sales have to be considered fairly disappointing," said Pinter. "Ben Carson's book is doing huge business, not just having sold 245,885 since publication in May, but it's still selling over 11,000 copies a week and has a good shot at the No. 1 spot on the New York Times bestseller list in its 14th week in release."

Ryan, who is considered a possible 2016 contender for the Republican presidential nomination, wrote the book to "challenge conventional thinking, renew the conservative vision for 2014 and beyond and show how it is essential for the well-being of our communities and the future of our nation," according to the publisher.

Ryan did not receive an advance from the book, per House rules, but the eight-term congressman will receive royalties from sales.

Since kicking off a book tour earlier this month in Philadelphia, Ryan has crisscrossed the country holding book events and speeches to tout "The Way Forward."

In Chicago, he had his first public event with Mitt Romney, who chose Ryan as his running mate in 2012.

Because Ryan is seen as a 2016 contender, his book will be seen as a gauge of his popularity heading into the national contest.

When former Secretary of State Hillary Clinton published her latest memoir, "Hard Choices," earlier this year, a great deal of attention was focused on how many books she sold.

Although Ryan outsold Clinton last week -- 6,266 to 3,910 -- the former first lady has sold 231,254 copies overall, according to Nielsen.

Clinton's book landed atop the New York Times bestseller list when it was released in June, but her sales were considered poor because of the sizable advance she received, the attention around the book rollout and the fact her publisher reportedly ordered 1 million first edition copies.

CNN reached out to a Ryan representative for comment but did not hear back.