If you own(original, 2011, 2012 or Ultimate versions) you'll be able to secure an impressive 50% off the sequel. Not to bad at all. Regular pre-orders carry a 20% discount.
Cities XXL packs in even more city-building options than its predecessor, including 47 architectural styles and over a thousand different buildings. This includes new ecological buildings and upgrades, like the park-and-ride, electric car dealership, and bike hire. Think green, everybody.
Your cities are part of a larger infrastructure, the ‘Cities Planet’, which means you can trade resources like oil, fuel, tourism and water between your cities across 65 different maps. And if that's not quite enough building for you, you can download a bunch of user crafted content via the Steam Workshop.