Free Series Starter:
Indecent Proposal (Book #1)
A Game of Billionaires (Book #2)
Main Series:
Rogue (Book #3)
Order (Book #4)
Prince (Book #5)
Royal (Book #6)
Reign (Book #7)
The first books (Indecent Proposal and Game of Billionaires) are free expanded samples of Rogue. They contain the first part of Rogue so you can read a longer, expanded sample rather than just what the “sample” allows.
The main series is the series order you want to read.