The book, called A Promised Land, was published on Tuesday and has already sold more than one million copies when audiobook sales are counted in.
Even though many have adored the complete autobiography, others have been left astonished by the fact it will take them more than a whole day to listen to it.
On Twitter, the former president has been called a "self-centered", a "narcissist", and "a legend in his own mind" over the very long autobiography.
Fox News pundit Tucker Carlson jumped in during a part on his show Thursday night, stating out that A Promised Land - which is 768 pages long - is the second memoir that the former president has written.
On Thursday night, Obama attended NBC's Jimmy Kimmel Live, where he protected the length of his book, saying when he started writing he did not mean for it to reach the final page number.
He also gloated to Kimmel that his book sold "a tad more" than former first lady Michelle Obama's book "Becoming", which was said to be 2018's fastest-selling book, selling 725,000 copies on the first day of publication.
Obama, 59, had written the 1995 bestseller, Dreams From My Father: A Story of Race and Inheritance.
"Two autobiographies before you're 60? It's safe to say he doesn't have a self-esteem problem," Carlson sharply said.
Obama is now in the midst of writing a third autobiography, which will detail the later part of his administration. It will be published someday in the next few years.
Meanwhile, comedian Adam Carolla appeared on Carlson's program and stated: "Obama is a bigger narcissist than Trump!" "I was only able to listen to the first 17 hours on the toilet this morning," he ridiculed.
In his Thursday night appearance on Jimmy Kimmel's show, the former president was humorously asked by the host "Did you make it that long to make sure Trump never reads it?"
"I don't think it would have had to be 700 pages," Obama joked in response, going on to explain he didn't intend for the book to be so lengthy, but that he wished to describe a variety of things from his presidency in detail.
"I want people to understand how I was making decisions, what we were dealing with... I didn't want to put everything in footnotes and endnotes," he said, admitting that he tends to skip footnotes when he discovers them in books.