A productivity expert shares 5 must-read books for anyone who wants to get ahead at work

Adrian Shepherd is a British productivity consultant who's lived and worked in Japan for the past 24 years.Through his work, he's kept his own library full of books on what it takes to be successful. It started out as a collection of business and productivity books, but soon it had a wide range of genres.While many of his favorites are best-sellers, there are a few excellent books on success that have slipped through the cracks but are worth reading, including “Blue Mind” by Wallace J. Nichols and “The Third Door” by Alex Banayan.Visit Business Insider's homepage for more stories.I used to think a library was a place you visited on the weekend to read books or a quiet place to study at school. Jim Rohn, the American business philosopher, taught me otherwise. He used to say, “Every house over $250,000 has a library in it. Why do you think that is？” That was the day I started my own library.First, it was a box in my closet. Today, my success library has swelled to over 700 physical books and another 800 online. I didn't limit my studies to just business and productivity, but added books on marketing, copywriting, psychology, linguistic programming, history, and nutrition.Read more: Microsoft CEO Satya Nadella shares the 3 essential traits that great leaders like Jeff Bezos, Bill Gates, and Mark Zuckerberg all have in commonI've got nearly every well-known book, including “The Seven Habits of Highly Effective People,” “The Four-Hour Work Week,” and “Rich Dad, Poor Dad.” They each sold millions of copies and helped spawn a series that made their authors well-known keynote speakers in every corner of the globe. While these books were game-changers, I'm always on the lookout for those books that slip through the cracks.Here are five books that didn't really get the attention they deserved.