I teach so I may be biased! I ask that the partners call to speak to me if they are a little skeptical (either parent!).
I only teach because I did the training for my baby and was completely blown away by it. I found it worked and worked well.
I find that generally it is the men who sit back in their chairs with arms crossed with a 'hmmmmmmmmm' look on their face in session 1. By then end of the session, when we show the videos, they are leaning forward looking amazed and excited. I think they are generally a bit more cautious as they don't want their partners to get their hopes up and be disappointed. They always come arounbd!
The difference between the book and the course is that with the (new UK version) book you don't get the practise CD. This is useful, and I don't know why they changed the format! I think the US version still comes with it. It is a good book though and gives you the philosophy and basics.
On the course, you do exercises and have some therapy to get you in the right emotional and mental state for the birth. It sounds a bit hippy-dippy, but if you go into any situation feeling calm, in control and even looking forward to it, the outcome will be far better than if you feel scared, anxious and not in control.
If he won't come, take someone else who will be there on the day - that is the key. The partner has a big job to do! You usually won't be able to book a course by yourself.
Look on youtube... (this one is a news story about it - not a birth). Lots of waterbirths on there!