I bought this new edition when I did my CELTA course and it's fantastic! The old edition is already really good and very thorough as far as the content goes. However, the big advantage of the second edition is the new layout. There are coloured headings, tables and boxes with examples which make finding specific content and reading in general much easier (especially for a visual learner like me).
I have used it a lot during the course and found the timelines especially helpful. There are also some exercises at the end of each chapter.
I can really recommend this book if you want to do a CELTA or similar English teaching course.