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When it comes to his reading habits, Bill Gates is an open book. As he does every year around this time, the brainy billionaire Microsoft co-founder has once again released his summer reading list. Unsurprisingly, it's comprised of challenging intellectual volumes -- no easy, breezy reads for the beach.

Think nerdcore science and math. Then think harder about mitochondria and the meaning of life. Gates says he did while poring over the books on his list, usually late at night.

“The following five books are simply ones that I loved, made me think in new ways, and kept me up reading long past when I should have gone to sleep,” he writes in a new post on his blog, The Gates Notes.

Here are the five books that made the cut for Gates’s summer 2016 reading list:

1. Seveneves, by Neal Stephenson

Why he recommends it: “The plot gets going in the first sentence, when the moon blows up. People figure out that in two years a cataclysmic meteor shower will wipe out all life on Earth, so the world unites on a plan to keep humanity going by launching as many spacecraft as possible into orbit … Seveneves inspired me to rekindle my sci-fi habit.”

2. How Not to be Wrong, by Jordan Ellenberg

Why he recommends it: “This book has tons of good stuff in it for non-mathematicians. [Ellenberg] updates you about the world of math, what advancements have taken place. His enthusiasm comes across.”

3. The Vital Question, by Nick Lane

Why he recommends it: “[Lane] argues that we can only understand how life began, and how living things got so complex, by understanding how energy works. It’s not just theoretical; mitochondria (the power plants in our cells) could play a role in fighting cancer and malnutrition.”

4. The Power to Compete, by Ryoichi Mikitani and Hiroshi Mikitani

Why he recommends it: “To me, Japan’s fascinating. In the 1980s and '90s, the Japanese were just turning out engineering and doing great stuff. How did they lose their way? Why haven’t these companies not been more innovative?”

5. Sapiens: A Brief History of Humankind, by Noah Yuval Harari

Why he recommends it: “There’s a lot of things about early human history that a lot of people haven’t been exposed to and [Harari] is good and succinct on that. He goes off in many directions, like ‘Are we happier than we’ve ever been?’ and a lot about robots. It’s got the broad framework. It’s a great book.”

For more book recommendations from Mr. Gates, check out his blog’s packed book section, which dates back to 2010.