This is the first book about the Three Seas Initiative (3SI) in English. Central European nations created the Three Seas Initiative - a forum to build strategic connectivity among each other in three areas: transport, energy, and digital. My book explains what the 3SI is, and why it is important for the UK and the US to be engaged as partners. PART 1 - describes the 3SI fund, projects, members, and its three pillars: digital, energy, and transport. Chapter 1 - 3SI Fund Chapter 2 - 3SI Projects Chapter 3 - 3SI Countries Chapter 4 - Digital Chapter 5 - Energy Chapter 6 - Transport PART 2 - describes the benefits from a full engagement of the UK and the US in the 3SI. I also explain why countries such as Russia and Germany are less interested in the success of the 3SI. Chapter 1 - US engagement in the 3SI Chapter 2 - UK engagement in the 3SI Chapter 3 - Germany & 3SI Chapter 4 - China & 3SI Chapter 5 - Russia & 3SI PART 3 - is about the historical background of Central Europe. More analysis about the Three Seas Initiative and Central Europe on the author's website: www.mariuszrozycki.co.uk