This series very closely ties in to and crosses over with the Phoenix Pack series.
Check here for suggested reading order.

       

Spiral of Need (#1) (Derren & Ally)
Review
Buy:  Amazon  |  Paperback  |  Audio

Force of Temptation (#2) (Jesse & Harley)
Review
Buy:  Amazon  |  Paperback  |  Audio

Lure of Oblivion (#3) (Zander & Gwen)
Review
Buy:  Amazon  |  Paperback

Echoes of Fire (#4) (Bracken & Madisyn)
Review
Buy:  Amazon  |  Paperback  |  Audio

Shards of Frost (#5) (Eli & Casey)
Review
Buy:  Amazon  |  Paperback  |  Audio