In order to make it in today's economic climate, it's important to think deeply - that is, longer than eight minutes - on yourself and your business. Some business books focus on developing traits that will lead you to the c-suite, but I find great advice doesn't discriminate and often translates across all levels. Whether you're a sole proprietor, have a small business of your own, or lead a team that makes up part of a larger organisation, consider stocking your bookshelf with the selection below to sharpen your mind and add to your business' foundation.