We all start somewhere, right? Starting with something simple and familiar is perfectly fine. It's neat that there were drawing tutorials in the book.
As you go forward, keep in mind that there's a reason that life drawing has always been a mainstay for gaining art experience. Replicating the world around you lets you start to explore new options. Aside from that, construction circles are great. Perhaps not as much with the style shown here, but in terms of free-form facial expressions and body positions.
