A lot of information has been released here: https://docs.unrealengine.com/5.0/en-US/RenderingFeatures/Na... and here https://docs.unrealengine.com/5.0/en-US/RenderingFeatures/Lu...

There is also a source code release if you want to dive into that level of detail: https://github.com/EpicGames/UnrealEngine/releases/tag/5.0.0...

I don't think the released details are that surprising to those working on realtime computer graphics, but the engineering details and tradeoffs are certainly interesting. Epic has the budget and business case to allocate a team, including some of the best graphics engineers in the industry, to do R&D for over a year to make this a reality.