See my review of this book, along with Jeff Goodell's How to Cool the Planet: "The Geoengineering Genie"

Update: On my review of Goodell's book, someone asked why I liked that book better than Hack the Planet. Here's my reply:

How to Cool the Planet is a much better read. If you don't know much about geoengineering, it's the better book to get. Perhaps I should have given it five stars...

However, if you have been following a lot of the news on geoengineering over the past couple of years, then much of the material in How to Cool the Planet will be old hat to you. It could still be fun to read—as it was for me—because of the insight into the personalities of the advocates of geoengineering research, like David Keith and Ken Caldeira.

If you're not so interested in personalities, and want more detail on the science, then Hack the Planet delivers that. However, it is not as smooth of a read, and assumes a science-literate audience, familiar with things like bell curves, which it brings up without explaining them.