The majority of the book describes the historical development of the concept of "superstition" in the Western world. Mainly, it is often used as a political tool to denigrate and persecute people with other belief systems. It's related to more than just the "unscientific" beliefs that its modern meaning usually denotes, and is deeply connected to all our major belief systems, including religion and science, which makes the reading both enlightening and entertaining.
Superstition has not always been negatively associated with religion or anything "unscientific" like today. Before the Enlightenment, it was mainly used derogatorily by the mainstream religion or beliefs against others. The Greeks used it for beliefs by the lower class, for foreign beliefs deemed exotic, or for what they considered magic. The Romans used it for Christianity until it became popular. Then, the Christians took that concept for pagans and heretics. Many of the accusations of superstitious practices, such as demon worshipping, were used for political struggles, instead of anything substantively deviant. Ironically, the Christian Church tolerated rituals and beliefs based on the Christian faith, but were otherwise not much different from other "superstitions" as defined by them. This lasted for centuries, until religious rebels turned the notion of superstition against Christianity itself, starting the Protestant Reformation. In the Age of Reason, the meaning of superstition shifted from bad religion to anything considered bad science, becoming closer to its meaning today. Notably, it's been used a lot with rise of spiritualism in America since the 19th century.
Contrary to Weber's claim of disenchantment, Vyse proclaimed, superstition and religion never went away. He gave examples of the superstitions that still exist around the world now and clarified the contemporary usage of the word: it is not religion and is not mental illness, and it is inconsistent with science, is instrumental and pragmatic, and is culturally fair. He discussed its association with people's stress and with their need for control. There are also some speculations of how superstition could come about and explanations of what's bad about it.
As clear from its history and from its contemporary definitions, "superstition" here is conceptualized in a very Eurocentric way. Although Vyse gave accounts of "superstitious practices" in non-Western cultures and argued it being culturally fair, the idea of framing a belief system as either science, religion, or superstition is very specific to the cultural developments of the Western world. Granted, this is a book written in English on a word in English, and due to the cultural proximity many other European languages and cultures share similar concepts (specifically, when discussing its origin the book does go back to Greek and Latin). Nevertheless, this introduction would be more comprehensive if it also includes ideas similar to but not necessarily identical with "superstition" in other cultures such as those of Asia, Africa, and indigenous America. How had other parts of the world viewed "superstition" within their own cultures, without the lens of modern science? Apart from the Western world, many of the cultural practices are based on beliefs that the locals (at least used to) consider truth and reality (just like science is considered truth and reality for many now), and they would have their own ways of dealing with "heresies." Listing those cultural practices out, while still calling them superstitions, does not make the survey unbiased, even though the cultures themselves might have already been influenced by the West by now.