Yes — each book builds directly on the previous. Start with Book 1. The Brothers Hawthorne (Book 4) is best read after the original trilogy.
The original trilogy (Books 1–3) is complete. The series continues with companion novels. New books in the Hawthorne world continue to be released.
The series is engineered for compulsive reading: every chapter ends with a revelation, the romantic tension between Avery and the Hawthorne brothers is intense, and the puzzle-box mysteries are genuinely clever. It rewards reading in one sitting.