I happened to learn ROOT in a class at our university and liked it from the beginning. The software comes with extensive documentation at CERN's homepage. However, I found that this is hard to understand for beginners. It also seems that ROOT is a software written by particle physicists for particle physicists. This makes parts of the documentation difficult to understand for people who are not that much into this subject but simply want to use ROOT for their area of research. This is why I decided to start a Wikibook about ROOT.
This book should serve as a first guide to people who want to learn ROOT. It should be open to people from any subject dealing with data analysis. After reading this book and doing the suggested examples people should be able to use elementary features of ROOT for their individual purpose and gain more expertise by consulting the official documentation.
I don't think that it would be wise to incorporate detailed explanation of the various classes of ROOT. This is done in an excellent way on its homepage. This book should prepare the reader to understand the original documentation in its concise form rather than preparing the documentation for the reader.
A word about language: I'm not a native speaker of English but I decided that English is the standard language of both, science and programming, so it would be the best idea to write this book in English. I'm sure that everybody who needs ROOT for his or her work will also need English for it. So I hope that also readers and authors from others than the English Wikibooks will join and find this book useful.
I know that writing this book will be a whole lot of work and any contribution will be warmly appreciated. Let it become good!