The objective of the LuaTeX project by Taco Hoekwater, Hartmut Henkel and Hans Hagen is to provide a versatile successor to TeX. During the development the team keeps track of ideas and experiments. In parallel ConTeXt MkIV is developed. This book describes the development of both systems and shows what impact the project has. The book start at version zero and ends with version 0.50, the first formal release.