That particular book of Scott's isn't a bad way to start out; although I do think there are better books out there that have been written since that particular one. I'd suggest "Wicca" by Thea Sabin or "Wicca: A Year and a Day" by Timothy Roderick as better alternatives.
Scott does make things approachable and easily understandable. And you can't blow your foot off (magically speaking) by doing any of the spells and rituals he includes in his books. So as a beginning book it isn't bad.
But there is one thing on which I strongly disagree with Scott. He makes the statement that Wicca is "anything you want it to be." That's just plain wrong and a bit silly. Wicca is a specific religion and it has some specific beliefs and practices that left out make what you're doing something other than Wicca. Other than that, I think he's OK as an author.