Getting Real by 37signals (available online) is a good mind stretcher. It provided much of the content for Rework (also by 37signals). Both books provided a lot of counter-intuitive business and development advice that works rather well in the software industry. Rework is one of my favorite business books with great illustrations (also available online).

Favorite chapters (from Getting Real):

• Build Less
• What's Your Problem?
• Embrace Constraints
• Be Yourself
• What's the big idea?
• Make Opinionated Software
• Half, Not Half-Assed
• Start With No
• Alone Time
• Meetings Are Toxic
• Get Defensive
• Less Software
• Zero Training
• Answer Quick
• Tough Love
• Publicize Your Screwups
• Better, Not Beta
• Beware the Bloat Monster

Maybe just read it all =)