If you are looking for resources to bridge the gap between grammar oriented teaching and communicative teaching, you should read this book. It will help you understand how to make your classes more communicative and interesting as well.
There are better books - Willis, Skehan, Ellis, Edwards and Willis. I read the original of this book, and the new updated version is definitely better. Nunan a lot of the time when he thinks he's talking about TBL is in fact really talking about PPP. I have read almost everything on TBLT and Nunan in my view is a very minor figure rather than one of the important researchers/writers in this area of methodology. I bet in the future his next article or book won't be on this subject. So based on all the above I give it 3 and say there are better books out there.