It's become an annual tradition. For the past several years, in mid-May, billionaire Microsoft co-founder Bill Gates has offered up a summer reading list, sharing it publicly on his  Gates Notes blog.

Gates paired this year's list with a video featuring cute puppies cavorting with his chosen titles. One dons an Abe Lincoln-style stovepipe hat for a book about Honest Abe, and another rides on a hospital gurney wearing a protective neck collar for a book about a divinity professor coping with her Stage IV colon cancer.

Gates has chosen books that can be enjoyed by readers of all professions -- you don't have to be a software genius or company founder to appreciate any of them. But in the extended summaries of each work, he's quick to point out how each book speaks to him, and many offer lessons that are especially pertinent to entrepreneurs and businesspeople. Here's this year's summer reading list.

1. Leonardo da Vinci, by Walter Isaacson

Top takeaway: Follow your sense of wonder, but don't go overboard.

Gates has a special fondness for the brilliant inventor and artist Leonardo da Vinci -- in 1994, he paid $30 million for one of Leonardo's scientific notebooks, now known again as the Codex Leicester. (Gates declined the chance to rename the notebook after himself, noting "I thought (Codex Gates) sounded silly.")

Gates singles out Isaacson's biography of the Renaissance legend for breaking down just exactly how special he was.

"The attribute that stands out above all else was (Leonardo's) sense of wonder and curiosity," Gates explains. "When he wanted to understand something--whether it was the flow of blood through the heart or the shape of a woodpecker's tongue--he would observe it closely, scribble down his thoughts, and then try to figure it all out."

But this intense focus could also go too far: The book explains that in the process of creating a statue involving a horse, Leonard learned so much about horses that he ended up creating new systems for feeding them as well as designing cleaner stables. Probably great ideas, but the statue was never completed.

Top takeaway: Don't get stuck on finding a reason -- bad things do happen to good people.

Divinity professor Kate Bowler was just 35, married and mom to a young son, when she was diagnosed with Stage IV colon cancer. Before her diagnosis, Bowler had written a book about the prosperity gospel, which Gates describes as "the idea popular among some Christians that God rewards the faithful with health and wealth." While she herself wasn't sold on that idea completely, her diagnosis shook it out of her head for good.

In addition to having to pursue the day-to-day treatment options that could help her survive to raise her son longer, Bowler had to grapple with some big questions, namely, Why me
Is this a test of my character?

Gates notes that Bowler "answers the 'why' question in a compelling way: by refusing to accept the premise." And he gets unexpectedly personal, discussing his own family life with a blunt and painful story.

"All four of my grandparents were deeply devout members of a Christian sect who believed that if you got sick, it must be because you did something to deserve it," he writes. "When one of my grandfathers became seriously ill, he struggled to figure out what he might have done wrong. He couldn't think of anything, so he blamed his wife. He died thinking she had caused his illness by committing some unknown sin."

Even if tragedy hasn't touched you, Bowler discusses how those trying to support someone who may be dealing with a diagnosis should veer away from judgemental and painful statements, and includes a list of six better ways to support them.

"If I could pick one thing, it would be that everyone simmers down on the explanations for other people's suffering, and just steps in with love," Bowler said in a TV interview.

3. Lincoln in the Bardo, by George Saunders

Top takeaway: Look carefully at the human consequences of decisions.

Think you know everything about Abraham Lincoln? The stovepipe hat, the log cabin, Ford's Theatre, the Gettysburg Address? Think again. The only novel on Gates' list, Lincoln in the Bardo, will shake up what you thought you knew.

The novel takes place over the course of one, long, sad night during which Abraham Lincoln visits the grave of his late son Willie, who died at just 11 of typhoid fever in 1862. Willie and his father were real, of course, but the events in the book are Saunders' fictional take on what the grieving president might have felt and said on a visit to Willie's tomb. More than 160 ghosts flit in, trying to convince Willie to leave the bardo, an intermediate space between life and rebirth.

"Despite being a work of fiction, it offered fresh insight that made me rethink parts of (Lincoln's) life," Gates writes. And it also made the Microsoft co-founder think heavily on the consequences of decisions.

"The president has a new understanding of the grief he's creating in other families by sending their sons off to die in battle," Gates writes. "He must make a choice. Should the war go on? If it does, how can we ensure the end result justifies the cost of such suffering?"

Top takeaway: Our world is interconnected, and it's not too late to learn about it.

Gates and scholar David Christian, the author of Origin Story, work together on The Big History Project. It's a program aimed at encouraging schools to use a social-studies curriculum known as Big History, and "big" is a good word for it. The course starts with the Big Bang and winds through more than 13 billion years of world history, integrating multiple perspectives in everything from chemistry to anthropology, all based on modern science.

"Origin Story is essentially the Big History course condensed into a short book," Gates writes. The course, and the book, divide that 13 billion years into eight "thresholds," or moments in time that mark major transition points, such as the first appearance of humans.

The course is taught in a slowly growing number of schools, and adults can join in with an online, self-guided, six-hour version. Or pick up the book, which Gates says contains "some things that are simply too new to be included in the course."

5. Factfulness, by Hans Rosling, with Ola Rosling and Anna Rosling Ronnlund

Top takeaway: Don't panic! At least not until you've broken down why you're scared.

As part of Gates' work with the Bill and Melinda Gates Foundation, he uses the terms "developed" and "developing" world frequently. But Factfulness, by the late Swedish global-health lecturer Hans Rosling, has taught the billionaire those terms aren't quite accurate.

One cannot simply divide the world into rich and poor, Rosling's book teaches. He compares it to looking down at other buildings from a skyscraper -- everything looks short from your height. To more clearly understand poverty and how to think about it in a helpful way, Rosling divides the world's population into four income groups. One billion people live at level one, sleeping on dirt and spending much of their days walking barefoot to get water. At the other end, a wealthier billion people own cars and can afford to take vacations. Understanding that framework can put poverty -- and the progress made to fight it -- in perspective.

The book is mostly devoted to explaining 10 instincts that help keep us from seeing the world "factfully." Scaremongering headlines can frighten unnecessarily, but breaking down the innate biases that lead us to overreact can lend us a well-needed perspective.

"These instincts make us human," Gates writes, noting that "overcoming them isn't easy." But he notes that Rosling refused to judge others for their misconceptions, wanting only to teach.

"If you never met Hans or watched one of his many TED talks, Factfulness will help you get a sense of why he was so special," he says. "I wish I could tell Hans how much I liked it."