A Treatise of Air is the second installment in the Edinburgh Doctrines series, written by the Scottish author CL Jarvis; and while it is a loose sequel to The Doctrines of Fire, it can be perfectly read as a standalone. We maintain the setting, Enlightenment Edinburgh, but changing some characters, losing our George Stephens, but gaining in exchange the Fulhame marriage; also passing from dark academia to a more conventional mystery with plenty of action.

Elizabeth Fulhame is aiming to get recognised with her chemistry experiments; a colossal task, taking into account that she is lacking many of the necessary equipment and that due to her genre, she's not really taken into account in an academical society ruled by men. She has hopes than once her husband, Thomas, finishes his medical degree, their situation improves and getting more equipment wouldn't be just a dream. When Dr Joseph Black tasks Thomas with receiving a French inventor who claims selling a valuable industrial dyeing process, the Fulhame marriage sees in this an opportunity to change their luck; however, the secret gets stolen by an English aristocrat.
Being this their best shot at scaling in Edinburgh's society, Elizabeth decides to steal it back with her wits and magical abilities; starting in the process a deadly cat-and-mouse game that will take them to the dangerous wynds and the high society balls of Edinburgh. She's risking much, but her goal is everything for her, and by extension, to Thomas.

In this second installment, we get the Fulhame marriage as the main characters, with whom CL Jarvis establishes a different dynamic than with our previous one, George Stephens; the chemistry and the complicity between Thomas and Elizabeth is certainly enviable. Elizabeth is dealing with the sexism attached to the academy, and she's looking for recognition, even if in the process she has to work harder than anybody; meanwhile, Thomas is just aiming to finish his degree.
Profesor Black and Cullen return in this novel, but they pass to a secondary role in comparison with the first one; it's particularly interesting to see their evolution towards accepting Elizabeth once they see their ability.

As we saw in the first book, the setting is one of the main selling points of this book, as Jarvis manages to create a really accurate portrait of Enlightenment Edinburgh; and in this installment we get to visit places that wouldn't be possible with George, examining other aspects such as the dyeing industry and the society balls.

In comparison, the pacing is slightly slower, but we are rewarded with more memorable scenes; still, a book that you devour naturally due to how well it is written. 

A Treatise of Air is an excellent second novel, which can be read as a standalone, in this historical fantasy series. If you like mystery and want to explore a historical period with a great amount of detail, give a try to this series.