A lot of what we take for granted and as firmly established scientific facts were either unknown back then, or still unproven theories, around half a century before the first man-made satellite would be orbiting our planet.
The author never speculates but describes everything based on what was then known as facts, and whenever he is dealing with something unproven, he says so.
The book is divided into chapters about such topics as comets and meteors, northern lights, seemingly completely black and void areas in the universe, the "unfixedness" of what we call fixed stars, the violent history of the Moon, and - maybe most fascinating of all for the modern reader - the possibility of past or present life on Mars.
Remember, this was written when the only means of observing the universe were telescopes based on Earth - no Hubble or James Webb space telescopes yet, and radioastronomy had not yet been invented. But photography was already widely used in science, and the author often refers to photographs to illustrate a certain point. My (free) kindle ebook came without any, but the way everything is described is good enough for the imagination without pictures.
An excerpt from the preface reads:
"The idea of the author is to tell about these things in plain language, but with as much scientific accuracy as plain language will permit, showing the wonder that is in them without getting away from the facts. Most of them have hitherto been discussed only in technical form, and in treatises that the general public seldom sees and never reads."
This "plain language" is rather poetic at times, and makes for very good reading, easy to understand for anyone remotely interested in astronomy without necessitating a degree in astrophysics.
It was not the first time I've come across Garrett Putnam Serviss. He lived from 1851 to 1919 and was an American astronomer as well as an early science fiction writer. And it was as the latter that I first "met" him: as the author of "A Columbus of Space", a book I have reviewed here..
I have mentioned above that the chapter about Mars is maybe the most fascinating part of the book. You have, I assume, heard the name Schiaparelli in connection with our neighbour planet. If not, let me just briefly tell you that it was by the Italian scientist (1835 - 1910) that the world first heard of "canali" on Mars - presumed channels for irrigation of the dry surface, built by the presumedly highly intelligent Marsians and clearly "seen" by Schiaparelli and many others, such as his American colleague Lowell (1855 - 1916), of equally scientific minds, through their telescopes.
We have long come to learn the truth about Mars - there are no channels, and never have been. But at a time when their existence was rarely doubted within the scientific community, Garrett P. Serviss wrote that most interesting chapter.
A lot of other things in the book have since been thoroughly examined and explained with the help of modern technology. We know a lot more about "solar wind", for instance, black holes and novae, and what comets are really made of. Still, it is interesting to see how people put their minds to explaining things as best as they could, with the means they had. And who knows how our up-to-date knowledge of astronomy will appear to a reader in another 100 years!