I second Dave's message. The Total Immersion book ( 2004 edition) was a milestone in my swimming. I think it is the best book on swimming I have ever read and I've read a few.
However, one of the great things about Terry Laughlin and the whole Total Immersion movement ( if that's the right word) is that he is very open minded and constantly looking for new and quicker ways to teach people to swim well and to be put on a path of constant improvement.
The newest books and DVDs incorporate a lot of revisions made as a result of feedback form TI students and teachers, and also probably from constructive criticism from elsewhere in the swimming world.
There is also destructive criticism out there.