Read the 4th edition of this book published in 2010 as a study guide for the NYS certification test in TESOL, as recommended to me by professionals in the field and a colleague who took the exam. It was often a good overview of concepts and issues involved with teaching English language learners, but I don't think it affected my performance on the exam I took, which was much more scenario- than fact-based. The only really helpful prep was the short guide available online where you register for the test.