Mastering the Core Teachings of the Buddha by Daniel Ingram
This book changed everything I thought I knew about meditation and the spiritual path in general. He tackles the taboos and myths around the concept of enlightenment, clearly and succinctly lays out the stages and paths that spiritual progress takes and draws parallels and comparisons between Vipassana (often called Insight Meditation in the west) and other spiritual traditions.
Just when I was about to give up on my meditation practice in despair and disgust, this book reconnected me with my practice. It explained in a tangible way why practice is worthwhile and made the whole process seem realistic and achievable.
I suspect this book will only be of interest to those with some meditation practice and theory behind them.
You can download an ebook and read it for free at: http://integrateddaniel.info/book/
Update Jan 2013: I'm halfway through reading this book again and I have to say it's even more amazing the second time through. Having had a chance to digest much of the material I'm stunned at how much more there was which didn't stick on the first reading.