Bill Gates is an avid reader who has recommended hundreds of books on his personal blog. Four books he's read recently, however, have had such a powerful impact on the founder, he said they've influenced how he thinks. "These books make me optimistic about the world and help me understand the role of innovation in driving progress," wrote Gates in a tweet earlier this month. Gates shared the four books on a list titled "Books that shaped how I think about the world" on Likewise, a mobile recommendation platform for books, TV shows, movies, restaurants and other entertainment. Likewise launched October 3, with support and funding from Gates. Other famous users of the app include Melinda Gates, Bono and Howard Schultz. Here are four books Gates said have shaped how he thinks.

"Energy and Civilization: A History"

Author: Vaclav Smil About the book: Gates has said he waits for new books from Vaclav Smil "the way some people wait for the next 'Star Wars' movie." In Smil's book, "Energy and Civilization: A History," the author and professor looks at world history not through rotating names of kings and queens but through how humans have harnessed energy from caveman days to the most sophisticated cultural and social advancements. Gates praised Smil's ability to capture the big picture as well as history's most remarkable details. "I'll admit that Energy and Civilization is not easy reading," wrote Gates on his blog. "In fact, when I read my first Smil books years ago, I felt a little beat up and asked myself, 'Am I ever going to be able to understand all of this.' But [the book] follows an easy chronological progression and is well edited." How it influenced him: Smil's book links energy consumption and economic growth. It's a connection Gates has seen as well and is one of the drivers behind Gates' work pushing for energy innovation. In this case, Gates says Smil's book made him feel even more optimistic about how soon the next generation in clean energy will be reached, "from carbon-natural liquid fuels to game-changing improvements in energy generation, storage and transmission."

"Enlightenment Now: The Case for Reason, Science, Humanism, and Progress"

Author: Steven Pinker About the book: "Enlightenment Now" is a comprehensive look at progress in world history. Pinker, a psychology professor at Harvard, puts data in context to show how health, prosperity, safety, peace, knowledge and happiness are on the rise worldwide. How it influenced him: Gates was already familiar with many of the topics in the book but appreciated the more "obscure" details Pinker uncovered to show how the world is changing for the better. Some of Gate's favorite details included how we're all less likely to be killed by a bolt of lightning than we were a century ago or how time spent doing laundry fell from 11.5 hours in 1920 to an hour and a half in 2014. "The world is getting better, even if it doesn't always feel that way. I'm glad we have brilliant thinkers like Steven Pinker to help us see the big picture," Gates wrote in a review of the book. This book "is not only the best book Pinker's ever written," wrote Gates, "it's my new favorite book of all time."

"Factfulness"

Author: Hans Rosling, Ola Rosling, Anna Rosling Rönnlund About the book: "Factfulness," explores why humans are consistently wrong about common problems facing the world. Instead of making decisions based off of facts and data, humans are largely influenced by unconscious biases. The book explores ten instincts that keep humans from putting the world into perspective, such as how we're more likely to pay attention to things that scare us or topics with impressive size and scale. Though he thinks everyone could benefit from the book, he said it was a must-read for recent grads. "I think everyone should read it. It has especially useful insights for anyone who's making the leap out of college and into the next phase of life," said Gates. How it influenced him: In "Factfulness," the authors offer a new framework for how to think about the world: instead of dividing the world into two wealth groups — rich countries and poor countries — the book proposes that there are actually multiple income group levels, ranging from the most extreme poverty where people cannot afford shoes to levels where people have running water or enough disposable income to take vacations. Gates says that viewing the world in this way helps to better detect progress. When the world is broken up between just rich and poor countries, it's easy to think anyone without a certain quality of life is poor, Gates wrote. "This was a breakthrough to me," explained Gates on his blog. "The framework Hans enunciates is one that took me decades of working in global development to create for myself, and I could have never expressed it in such a clear way. I'm going to try to use this model moving forward."

"Sapiens"