There are 3 books by Marguerite O'Callaghan on BookOrb. A strong starting point is This Dark Town I (2017). The bibliography below is in publication order, with series grouped in reading order.
Standalone books
Frequently asked questions
How many books has Marguerite O'Callaghan written?
BookOrb lists 3 books by Marguerite O'Callaghan.
Where should I start with Marguerite O'Callaghan?
A good starting point is This Dark Town I (2017).
What is the Marguerite O'Callaghan books in order list?
In publication order: 1. This Dark Town I (2017), 2. This Dark Town II (2017), 3. This Dark Town III (2018).