Three of my series take place in the same fictional universe. The Mad Mick, The Borrowed World, and Locker Nine are all about people in roughly the same geographic area experiencing the same event from different perspectives.
For the most part you’re fine to read each series in numerical order but there are two exceptions.
One, the Mad Mick character first appears in the second Locker Nine book, Grace Under Fire, so you get additional backstory on the Conor Maguire character if you read Locker Nine through book two before digging into Mad Mick.
Second, in book six of the Mad Mick series, Ultraviolent, the Mad Mick character has an encounter with the folks from The Borrowed World series. In the Borrowed World timeline, this meeting takes place between book 8, Blood and Banjos, and Book 9, Resurgent.
Some Borrowed World readers have been sending me messages wondering how they missed some of the details discussed in Resurgent and that’s the answer: they took place outside of the series, in Mad Mick 6, Ultraviolent.
Sorry if this caused you any confusion!