This book investigates the political-economic implications of changes in EU-Russia gas trade mechanisms resorting to qualitative and quantitative tools and combining Transaction Cost Economics (TCE), New Institutional Economics (NIE), and International Political Economy (IPE). Transformations in EU-Russia gas trade mechanisms have benefitted the EU and Gazprom’s revenues have been dented. However, the negative impact on Russian economy and federal budget has been limited. The last word is not said: should certain circumstances arise in future, these transformations might turn out to be detrimental for the affordability and security of gas supplies to the EU.