Recommended (in order):
1. Eaarth: Making A Life On A Tough New Planet by Bill McKibben (2010). Lucid and affecting, it drives home how we have changed our planet, and what that means for the future. An excellent introduction to the subject.
2. Heat: How To Stop The Planet From Burning by George Monbiot (2007). A rigorous and unsparing assessment of how major cutbacks in greenhouse gas emissions could and must be made. [my mini review]
3. Six Degrees: Our Future On A Hotter Planet by Mark Lynas (2008). A degree-by-degree breakdown of climate effects from one to six degrees Celsius of global warming, with a global scope. Fascinating and fearsome. [my review]
4. Field Notes From A Catastrophe: Man, Nature, and Climate Change by Elizabeth Kolbert (2006). Concise, enthralling, and at times unexpectedly funny. Might be my first choice but for how far climate science has progressed since it was written. [my mini review]
5. The Hot Topic: What We Can Do About Global Warming by Gabrielle Walker and Sir David King (2008). Straightforward and unsentimental, this book addresses the science, engineering, and politics of climate change by turns. A strong second choice for an introductory text, and especially well-suited for responding to (or giving to) skeptics.
6. The End of the Long Summer: Why We Must Remake Our Civilization to Survive on a Volatile Earth by Dianne Dumanoski (2009). Sets climate change within its broader environmental, economic, and historical contexts; seeks the deeper cultural causes of, and responses to, our planetary crises.
7. Censoring Science: Inside the Political Attack on Dr. James Hansen and the Truth of Global Warming by Mark Bowen (2008). An inside look at political manipulation of science under the George W. Bush administration, and a primer in the history of global warming science. [my review]
Deep Economy: The Wealth of Communities and the Durable Future by Bill McKibben (2008). Well-written, and contains some intriguing case studies, but not as essential as Eaarth.
Hot: Living Through The Next Fifty Years on Earth by Mark Hertsgaard (2011). Ambitious but technically uneven; at times I found it cloying. At its best when Hertsgaard lets the people's he's interviewing -- scientists, politicians, activists, engineers, and businesspeople -- take the fore.
In one of my book review diaries, someone said a book I reviewed was going on "the list." Another commenter asked to see that list. This diary is my response.
I put the 'Recommended' books in numerical order because it might be useful for busy people, but I consider them all good or excellent. Which you should read depends on your particular interests. e.g., if you wanted to know how the second Bush administration interfered with NASA scientists, you'd read Censoring Science; if you wanted to know how industrial societies could drastically cut greenhouse emissions, you'd start with Heat.
The 'Other' books are by no means bad; in my opinion they just aren't quite as good. Of course your mileage may vary, and any book that brings people closer to understanding and action is a good book.
I am conscious that my readings so far skew white (appearing) and male, and that the writers are all American or British. (Also, there seems to be a heavy representation of authors named Mark.) Because of this, I would especially appreciate reader recommendations of books on climate change written by women, indigenous people, people of color, and/or people from developing nations or the global South. (Of course, many authors do write about the effects of climate change on poor nations and communities, and relay the comments of selected citizens, but that is not the same as getting their perspectives and insights unmediated.)
Links provided for convenience and further information, but if your local bookstore or library system carries these titles, please consider picking them up there.
And please share your own recommendations.