Billionaire — and bookworm — Bill Gates has announced his latest reading recommendation, and it’s based on the principals of the man who first taught him to be a good manager.

While Gates is now admired as an influential business leader, it wasn’t always that way. In a blog post published Wednesday on Gates Notes, the Microsoft co-founder fesses up to a mistake he made when the company, founded in 1975, was young.

“In the early days of Microsoft, I felt pretty confident about my coding skills, but I had a lot to learn about project management,” Gates admits. “This became abundantly clear after an incident in 1978, when I told Intel — a really important customer — that we would deliver them a version of Microsoft BASIC in four weeks. They thought I was crazy to promise it that fast, and it turned out that they were right. We were two weeks late.”

Luckily, there was someone at Intel who could give him guidance. Gates says former Intel CEO and chairman Andy Grove helped him hone his management skills, adding that he is “one of the great business leaders of the 20th century.”

Grove, “A precise, hard-driving guy,” according to Gates, “…championed the idea of management by objective.” Grove penned a number of well-received management books, including “High Output Management” in 1983 and “Only the Paranoid Survive” in 1999.

Grove, who died in 2016, laid the groundwork for a popular management system called OKRs (objectives and key results). Big companies like Amazon, Google, and Netflix, as well as The Gates Foundation, have adopted the management trick.

Now, John Doerr, who also worked at Intel in the ’70s and is a venture capitalist at Kleiner, Perkins, Caufield & Byers (and an original investor and board member at Google and Amazon), has written “Measure What Matters: How Google, Bono, and the Gates Foundation Rock the Work with OKRs.” The book delineates “how OKRs work and shows how you can apply them in all sorts of situations,” according to Gates. He recommends it for “anyone in interested in becoming a better manager.”

“Objectives define what we seek to achieve; key results are how those top-priority goals will be attained with specific, measurable actions within a set time frame,” the book’s description on Amazon reads. “Everyone’s goals, from entry level to CEO, are transparent to the entire organization.”

OKRs are often touted as a way of keeping employees focused and on track, with objectives steering direction and key results being measurable achievements. For example, your objective might be to become the best dog-walking provider in New York City, while your key result is to secure 10 new clients by the end of June.

The book’s Amazon profile has reviews by business leaders including LinkedIn co-founder Reid Hoffman, Intel co-founder Gordon Moore and Facebook COO Sheryl Sandberg. Sandberg writes that Doerr has, “taught a generation of entrepreneurs and philanthropists that execution is everything.”

Don’t miss: Bill Gates says he’s ‘obsessed’ with this new website — here’s why