Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming, edited by Paul Hawken. Want to know where to make an impact? This book is the output of a scientific foundation analyzing how best to reduce global warming by 2050. It's a ranked list of things we as a global society should do, their costs and savings, their impact, and excellent introductions to each method. See also drawdown.org.
Hot, Flat, and Crowded by Thomas Friedman. This is the one I'd recommend to people looking for the big-picture context. It summarizes the main thrust of several of the books I've read and puts it into a geopolitical context. My favorite argument: Americans need a tax on carbon emissions because right now, by heavily subsidizing oil, we're already paying this tax (in effect) but to oil dictatorships rather than to our own country. Quick caveat: the author's tone works better as an audiobook.
Energy for Future Presidents by Richard Muller. This is the best book I've found for people with engineering interests who want to understand the available energy technologies, their likely impacts, and their current challenges.
What Can a Technologist Do about Climate Change? (A Personal View) by Bret Victor. Detailed, illustrated, and actionable essay on how techies and entrepreneurs can work on the problem of climate change.
This four-part series by Ramez Naam takes a look a the practical application of the current state of renewables technology, showing how it can be used and how we can improve it for better efficacy: How Cheap can Solar Get? Very Cheap Indeed, How Steady can Wind Power Blow?, How Cheap can Energy Storage Get? Pretty Darn Cheap, How Cheap can Electric Vehicles Get?
This cartoon is my favorite, briefest argument for action in the environmental space.
Vaclav Smil’s book Energy Myths and Realities (2010) is excellent for those looking to have their things-will-work-out-fine dreams shattered. It's a great place to start if you want to find the reasons to not be complacent about much-touted advances. It's not, however, built to inspire. Here's my blog post synthesizing Smil's harsh cynicism into opportunity spaces.
This Changes Everything by Naomi Klein. Not an easy read, but sweeping and loaded with examples and reference material. This thorough book looks at the environmental movement from several different angles. Klein is highly opinionated, so the challenge is in parsing out her biases versus widely held opinion.