The idea behind this book is a simple one. It suggests that in order to help your child's language development, you should dedicate 30 minutes a day to give them 100% attention (which has to be a good thing regardless of whether or not it helps their language). It explains how language is learnt, and how to use those 30 minutes to best effect.
The suggestions include things like making sure there is no background noise (young children can't distinguish between background and foreground noise); commenting on what your child is doing, not trying to direct his/her focus of attention, not asking questions, but making listening fun (eg by making silly noises and playing games). Using lots of repetition, and always responding to what your child means, even if it isn't expressed as 'speech'.
The book is arranged chronologically - so it tells you how to work with a child during the first 6 months, then 6-12 months, etc. In terms of advice, the chapters contain a large amount of repetition - ie, the techniques you use for a 6 month old aren't massively different from those you use with a two year old. So in a way, I felt the book could have been much shorter, but on the other hand, having all the information in every chapter does make it easy to dip into.
Although I think the content was good, I also think the main ideas could be summed up in a magazine article, rather than in a book of a couple of hundred pages. Also, as a mother of 18 month old twins, I found the one to one sessions didn't work too brilliantly. I tend to try and spend most of my day with my kids anyway, and they didn't seem to value their separate time with me, and didn't like being left with a neighbour (or whoever) whilst I did my one to ones with their sibling. So at the moment, I've put the one to ones on hold (I might go back to them in the future) but I do use the techniques recommended by Sally Ward now in my every day interactions with them, almost as second nature.