Also it's not a mystery. We can observe and measure it. We can write simple equations to accurately predict how it will behave. Our entire modern world is built around knowing how electricity worksI want to expand on this a little bit more (I had already done so, but the forum ate most of my post on mobile, grr).
So the article opens right up by saying, "Electricity is a mystery."
First of all, for a book that is supposed to be about informing and educating people (even those who are only at a 4th grade level -- ~9yrs old for non USAers) about electricity, it sure is quick to throw its hands in the air and shout, "We give up, we have no idea how it really works, where it comes from, how it's made, it's way too complicated, here are some guesses, whatever."
But second of all, the word choice here is key. The article says that electricity is "a mystery." There is specific religious meaning attached to the word "mystery," which is sometimes used interchangeably with "sacrament" and can be taken to mean "...a reality imbued with the hidden presence of God."* Try reading through the paragraph again, but this time substitute "[the] hidden presence of God" wherever you see the word "electricity" and it will take on an entirely different character, one where a "science" textbook essentially tries to tell you that the reason electrons move is [most likely] because God so wills it. It then finishes up with a Psalm quote chosen to basically drive home the idea that "Electricity = God."
This textbook is not designed for education, it is designed for indoctrination.
*see below"The Church is a mystery. It is a reality imbued with the hidden presence of God. It lies hidden within the very nature of the Church to be always open to new and ever greater exploration." These words, stated by Pope Paul VI in his opening address to the second session of Vatican II, capture the very heart of one of the central documents of the Council: The Dogmatic Constitution on the Church.