Bill Gates is fascinated by Theranos. Now he's recommending everyone read a book about the 'money, medicine, and mystery' of blood.

• Bill Gates has a fascination with blood - specifically, diagnostic blood tests that can detect diseases like Alzheimer's and cancer.
• For the past two years, Gates' book recommendations have reflected this interest.
• Last year, Gates recommended "Bad Blood," the story of blood-testing startup Theranos, which deceived its investors, patients, and business partners into believing its technology actually worked.
• This year, Gates has listed "Nine Pints," a book about the "money, medicine, and mystery" of blood, on his summer reading list.
• Visit Business Insider's homepage for more stories.

In just a few short years, Bill Gates' online book recommendations have garnered an "Oprah effect," helping to boost sales and spread the word about lesser-known authors.

But when Gates recommended "Bad Blood: Secrets and Lies in a Silicon Valley Startup" at the end of last year, the world was already familiar with Theranos, the blood-testing startup that deceived its investors, patients, and business partners into believing its technology actually worked.

Read more: 16 books about the biggest business scams of our time - including Enron, Bernie Madoff, and Theranos

The company's founder, Elizabeth Holmes, catapulted to fame around 2014 with her steely speech at the TEDMED conference and solemn portraits on the covers of various business magazines. By 2018, Holmes was forced to step down as CEO after being indicted on wire fraud charges.

By the time Gates got around to praising "Bad Blood," it had become fodder for an HBO documentary and upcoming feature film. Like many, Gates was captivated by the book's suspenseful twists and turns as it chronicled Holmes' efforts to salvage a failing technology.

The book even achieved the feat of keeping the billionaire glued to his chair.

"There's a lot Silicon Valley can learn from the Theranos mess," Gates wrote on his blog. "A rock star CEO can be a huge boon for a startup. But you can't let fame become the most important thing."

Though Gates said that Theranos represented "the worst-case scenario of what happens when a CEO prioritizes personal legacy above all else," he also worried that "Bad Blood" might "scare people away" from noninvasive diagnostic testing, which he has called "the future of health care." In recent years, Gates has invested money in blood tests designed to detect diseases like Alzheimer's and cancer.

This year, he's recommending a book that's a bit more optimistic about the future of blood testing. Among his summer book picks is "Nine Pints: A Journey Through the Money, Medicine, and Mysteries of Blood."

The nonfiction title is written by a woman with premenstrual dysphoric disorder, a condition that causes severe pain and mental anguish before getting her period. The author's struggle sets off a journey to understand how blood is commoditized, transmitted, and treated in various societies throughout history.

Eventually, she lands on the very subject that ignited the Theranos debacle: liquid biopsies, or using blood tests to detect and diagnose health problems.

"Nine Pints" makes no mention of Theranos, most likely because it focuses on the heroes of blood technology and the places where this technology is absent. But it does offer some "blood-boiling" anecdotes, according to Gates.

"The book is packed with super-interesting facts that I had to work very hard not to share with unsuspecting friends and colleagues during social occasions," Gates wrote in his blog. The billionaire was surprised to learn, for example, that blood is one of the world's most heavily traded commodities, costing around $67,000 a barrel.

While Theranos was a cautionary tale of what happens when blood technology wind up in the wrong hands, Gates said "Nine Pints" showed the ways in which learning about blood can lead to life-saving innovations.