I took the multi-week course a few years back and found it very helpful. I'm a very shy person and it helped pull me out of my shell a bit and be a better communicator. The course work was geared towards the business world but most lessons could easily apply to the personal world. Reading the book would be somewhat useful but I found the interactive nature of the instructor-led classes to do a better job at practicing the skills in a more real-world setting with constructive feedback.
It was pretty expensive from what I remember. Most of the folks in my class were covered by their employer but a few of us were (me, for one) paid our own way. They tend to discount from the listed price if asked, though. IMHO, the cost was worth it. I credit that course with helping me be much more assertive at work and reaching for higher paying opportunities.