Learning to effectively communicate with others is the single most important skill you can learn. It will help you improve your relationships with others, clearly communicate your own ideas, and address areas for improvement in ideas and others in a way that is constructive. There's been quite a few great books on this thread already. Here's some I haven't seen.

* The Ultimate Sales Machine - Chet Holmes - good even if you're not in sales

* The Effective Executive - Peter Drucker - Great book overall

* The Phoenix Project - good for understanding project flows and silos.

* Thinking in Systems - good for how to set up processes so that even if you step away the job still gets done. Essential for getting promoted, no one can promote you if you're impossible to replace.