What do you think of total immersion?

I just got Total immersion book yesterday. Have read part 1 of the book and just started doing the drills today. It seems an excallent way to swim and definatly will improve my f/s. But i'm a bit weary because it's so comercail. so my question is, Is Total immersion as good a way to swim as it makes out? or is it the best way to learn how to swim? Are there better books out there that teach you how to swim well(properly)? Hope that makes sense Swifty