This book addresses twenty-one themes related to the teaching of English as a second or foreign language, and is organized around a series of key questions. For example, 'How many words do learners need to know?', 'Do rules help you learn a language?' and 'Where do errors come from?' Based on a very popular blog, the author has re-crafted the original posts to take into account the discussion that each one provoked. So that the book can be used in a training context, he has also added eight discussion questions to each theme, as well as a full list of references, and links to the relevant posts on his blog. Each theme is attractively illustrated with original designs by Piet Lüthi.