Bill Gates just revealed his 2 favorite books of 2018 so far

REUTERS/Rick Wilking

Microsoft co-founder and philanthropist Bill Gates, pictured on May 6, 2017.

• Bill Gates just revealed his favorite books of 2018.
• The first is from one of his all-time favorite author, Harvard psychologist Steven Pinker.
• The other is being published in April posthumously by a Swedish physician.
• They're both extremely hopeful reads.

Bill Gates has never been able to pick just one book.

So during an AMA session on Reddit Tuesday, when a questioner asked Gates about the best book he'd read so far this year, Gates named two:

"There are two amazing books. One is Enlightenment Now by [Steven] Pinker and another is Factfulness by [Hans] Rosling," Gates wrote. "They are both very readable and explain that the world is getting better."

Pinker has been a Gates favorite for years. In Pinker's book, which was released earlier this month, he argues that people are happier, healthier, wealthier, and safer than they've ever been. He says that's not just true in the US; it holds up around the world.

Gates actually de-throned his old favorite book of all time, "Better Angels" - another Pinker book - to make room for Pinker's new "Enlightenment Now" at the top of Gates' all-time favorite books list.

Here's what Gates had to say in praise of his new #1 book, on his blog:

"Enlightenment Now" takes the approach [Pinker] uses in 'Better Angels' to track violence throughout history and applies it to 15 different measures of progress (like quality of life, knowledge, and safety). The result is a holistic picture of how and why the world is getting better. It's like 'Better Angels' on steroids."

The other book Gates is recommending comes from Swedish doctor Hans Rosling, who was an advisor to the World Health Organization and UNICEF. Rosling also helped set up Médecins sans Frontières in Sweden.

Roslin died in February 2017 at 68 years old, but his children finished up the final chapters of his book for him, and it's set to be released this April. It's called "Factfulness" and details ten of the most common ways we're wrong about the world.

"This book is my last battle in my life-long mission to fight devastating ignorance," Rosling said in 2017, days before he died.

Gates called it "an indispensable guide to thinking clearly about the world" and his wife Melinda echoed the praise: "Hans Rosling tells the story of 'the secret silent miracle of human progress' as only he can," she wrote in her review.

Bill and Melinda Gates were good friends of Rosling's, and before he died, he had one last request, which the couple detailed on Bill Gates' blog last February.

"He simply hoped that we would promise to keep spreading the message he was so passionate about: that the world is making progress, and that policy decisions should be grounded in data," they wrote.

Both Gates picks fulfill that dying wish. They are extremely hopeful books - both suggest, in their own way, that we're living in the best moment humans have experienced yet on Earth.

It's a trend that Gates, in his characteristically optimistic way, expects will continue. To aid that trend, Gates funnels billions of dollars toward fighting some of the world's most desperate problems, like advancing child and maternal health, improving education and working on eradicating extreme poverty.