Source: ABC.
Donald Trump has revealed Barack Obama's parting words to him in his first TV interview since being sworn in as the 45th President of the United States of America.
Mr Trump told ABC News' David Muir that a letter former US president Obama left for him in a drawer of the Oval Office was "beautiful".
"I won't show it to you (or) read it to you, but (it's) just a beautiful letter," Mr Trump said.
Former President Barack Obama could rake in more than $26 million in advance for his post-presidential memoir.
According to the Hollywood Reporter, Esther Newberg, co-head of ICM Partners' publishing unit, claims that an Obama memoir would "go for more than any president's memoir has ever gone."
Asked about his post-presidencyplans, Obama said he writing a book would be a "top priority."
His first novel, Dreams From My Father, was a bestseller when it was published in 2004.
(He is also the author of The Audacity of Hope, published in 2007 and the children's' book, Of Thee I Sing: Letters to My Daughters, which was published in 2010.)
Bush and Clinton sold 2.6 million and 2.2 million copies of their books, respectively.
Princeton University presidential historian Julian Zelizer told the Hollywood Reporter that he thinks sales for an Obama book will top both.
"There is broader fascination with Obama, from conservatives who really hate him as well as liberals who deeply admire what he did," he said.
There's also speculation that Michelle Obama could get her own book deal that would rival her husband's.
Hillary Clinton received $10 million for her memoir, Living History.
Literary agent Raphael Sagalyn told the New York Times last September that Obama could earn as much as $30 million for a two-to-three post-presidency book contract.
"His is going to be easily the most valuable presidential memoir ever," he said. "And I think Michelle Obama has the opportunity to sell the most valuable first lady memoir in history."
Presidents throughout the years have written books while in office and after leaving the presidency.
Theodore Roosevelt, who was in office from 1901 to 1909, authored nearly 40 books between 1882 and the year of his death, 1919.
Besides Obama, Roosevelt, Eisenhower and Trump, the only other president to write a book before entering the presidency was George H.W Bush.
He wrote the book Looking Forward in 1987, while he was serving as vice president.
Other presidents who have written books include Jimmy Carter, Richard Nixon, Ronald Reagan and Thomas Jefferson.
Current president, Donald Trump, is credited as an author on 18 books written between 1987 and 2015, the most recent being Crippled America: How to Make America Great Again.
