I meant to pick 10, but even though these 9 stood out, I had a harder time picking number 10 from a larger pool, (and I'm too modest to suggest my own book). I will try to put in some link beneath each book to some sort of resource. Thus, in no particular order:

Wilkinson & Pickett - The Spirit Level: Wilkinson and Pickett sums up large amounts of research that discloses how social inequality creates unhealthy societies on a huge variety of areas. Many areas, including health and crime suffer in unequal societies.
http://www.equalitytrust.org.uk

Daniel Pink - Drive: Dan Pink reads like he is writing for the business class airport-shopping readers, but his book sums up large amounts of research on how economic incentives ruin our intrinsic motivation, and creates poorer quality of the work performed. This book kills homo economicus and New Public Management both, once and for all.
http://www.danpink.com/books/drive/
http://www.youtube.com/watch?v=u6XAPnuFjJc

Oreskes & Conway - Merchants of doubt: This book discloses how powerful financial and ideological interests manipulates the status of science in the public sphere. Most notably on climate change, but also on heath effects of tobacco, use of DDT etc. A well-documented expose of how right-wing think tanks consciously manipulate science.
http://www.merchantsofdoubt.org

Antonio Santucci - Antonio Gramsci: Gramsci is essential to understanding political struggle in modern societies. Santuccis book gives a good overview of Gramscis life and work, including central terms like "hegemony", "common sense", "intellectuals", "war of position" and much more.
http://www.internationalgramscisociety.org

Joel Bakan - The Corporation: Bakan shows us how the destructive behavior of modern corporations is not the result of "greed" or of immoral individuals, but a logical consequence of the legal framework they are governed by in most western countries. It thereby also effectively kills "corporate social responsibility" as an alternative to political an legal regulations.
http://www.joelbakan.com/thecorporationbook.htm
http://www.youtube.com/watch?v=Y888wVY5hzw

Nelson Mandela - Long Walk to Freedom: This is much more than just Nelson Mandela's autobiography. It is also a thorough description of social changes that can be lessons for us still today. The way in which South Africa's slow development towards a more liberal and democratic society was halted and reversed when the Nationalist Party gained power is one such lesson. By enhancing racial conflicts they used the same conflicts to secure continued support. In a milieu where right-extreme forces once again grow in Europe. This is an important lesson. Another lesson from Mandela is that of which political forces actually supported the liberation of South Africa, and who worked against it.
http://archives.obs-us.com/obs/english/books/Mandela/Mandela.html

Adam Hochschild - King Leopold's Ghost: Hochschilds tale of the brutal colonial history of the Congo, is a warning to all of us. One lesson it teaches us is the tale of how people are capable of the most cruel and inhumane slaughter of other humans, and it tells it just as well the history of WW2. Another lesson is how this slaughter is driven by private profit-seeking businesses (rubber trade), under the guise of "civilizing". The result was the death of millions - about half the population of the Congo. Never believe the altruistic pretexts the powerful give for their imperial adventures.
http://www.ustream.tv/recorded/527424

Chomsky & Herman - Manufacturing Consent: In a way you could see this volume as a follow-up on Gramscis thought about a "war of position", exposing how a hegemonic world view can be created and maintained in a "free" society. (It should perhaps be updated to reflect the adjusted situation in a digital age. Then again- perhaps not.)
http://www.youtube.com/watch?v=Ci_1Ghk0CIc
http://www.thirdworldtraveler.com/Herman%20/Manufac_Consent_Prop_Model.h...

Thomas Piketty - Capital in the 21 Century: This book is so recent (at least its English edition), that I must admit I haven't finished reading it yet. However, this project is so central to the understanding of the state of the world today, that I will not hesitate to recommend it based on what I have read so far, and what others have written about it. As The Spirit Level is the empirically founded story of the consequences of inequality, Capital is the story of the reasons for the inequality.
http://piketty.pse.ens.fr/en/capital21c2