The Microsoft founder raved about Paul Kalanithi’s posthumous When Breath Becomes Air in a recent post on his personal blog. Gates is a well-documented book lover, but he said that his latest read managed to make him legitimately cry.

“I’m usually not one for tear-jerkers about death and dying — I didn’t love The Last Lecture or Tuesdays with Morrie. But this book definitely earned my admiration — and tears,” Gates wrote.

When Breath Becomes Air is Kalanithi’s memoir about his journey through medical school and eventual battle with stage IV lung cancer, which claimed his life in March 2015 when he was 37 years old. The book was published 10 months after his death and has since gone on to become a New York Times bestseller.

“It’s an amazing book,” wrote Gates. “I was super touched by it, as was Melinda and our daughter Jennifer. In fact, I can say this is the best nonfiction story I’ve read in a long time.

“I don’t know how Kalanithi found the physical strength to write this book while he was so debilitated by the disease and then potent chemotherapy,” Gates added. “But I’m so glad he did. He spent his whole brief life searching for meaning in one way or another—through books, writing, medicine, surgery, and science. I’m grateful that, by reading this book, I got to witness a small part of that journey.”