I write software for a living in a very coddled environment, far, far from any customers or marketing decisions (my company means well, but they are stilll catching up to the Cluetrain). Seth's blog, which led me to Unleashing the Ideavirus, is a peek into the nebulous world of human beings and the way to create products they like. Actually, Ideavirus is about creating products that people like and really want to tell other people about. Actually actually, Ideavirus is about creating products that people have to tell others about, just by using the product (like Hotmail, which was a truly innovative product before Microsoft purchased it). In contrast, something like a massage makes for a bad ideavirus because it's hard to explain the benefits to others and it's not immediately obvious to people that you've had a good one (although Sister Ros, a neighbor of mine, has done just that, by providing public massages at St. Paul Saints games for over a decade).
The book is repetitive, as most business books are, but in this case I didn't mind. If you have a product in mind, but aren't entirely sure how your product is going to spread from customer to customer effortlessly, read the book. Godin explains his point from several angles, giving your subconscious plenty of opportunities to turn your idea into an Ideavirus while you read.