Is clean hydrogen truly transformative for decarbonisation, or simply the latest energy hype? This book offers a clear, evidence-based examination of hydrogen's real role in the global drive for decarbonisation. It begins by explaining why hydrogen matters for climate policy and where electrification alone falls short. The early chapters assess hydrogen production technologies and costs, separating realistic pathways from overly optimistic assumptions. The book then explores policy design, investment incentives, and the regulation of transport, trade, and storage infrastructure. Later chapters analyse hydrogen's potential across key sectors, including power generation, transport, steel, cement, chemicals, and high-temperature industrial processes. The concluding section brings these insights together, highlighting trade-offs, system integration challenges, and lessons for policymakers. Written for policymakers, industry leaders, investors, and researchers, this book shows why clean hydrogen is important for a credible, cost-effective energy transition, even if it will not become the "next oil". Aliaksei Patonia is a Research Fellow at the Oxford Institute for Energy Studies, specialising in commercial hydrogen development. With a background in energy economics, sustainable development, and policy, his current research explores hydrogen economics, power-to-hydrogen technologies, infrastructure development, and applications in hard-to-abate sectors. Rahmatallah Poudineh is Head of the Electricity Research Programme at the Oxford Institute for Energy Studies. Trained as an economist and engineer, his research focuses on power-sector regulation, renewable support mechanisms, and hydrogen markets.    >