Spirit Animals has two main series, and three special editions (so far announced).
Books by release date
First series (Spirit Animals)
Book 1: Wild Born by Brandon Mull
Book 2: Hunted by Maggie Stiefvater
Book 3: Blood Ties by Garth Nix & Sean Williams
Book 4: Fire and Ice by Shannon Hale
Book 5: Against the Tide by Tui T. Sutherland
Book 6: Rise and Fall by Eliot Schrefer
Book 7: The Evertree by Marie Lu
Second series (Fall of the Beasts)
Book 1: Immortal Guardians by Eliot Schrefer
Book 2: Broken Ground by Victoria Schwab
Book 3: The Return by Varian Johnson
Book 4: The Burning Tide by Jonathan Auxier
Book 5: Heart of the Land by Sarah Prineas
Book 6: The Wildcat's Claw by Varian Johnson
Book 7: Stormspeaker by Christina Diaz Gonzalez
Book 8: Unnamed
Tales of the Great Beasts by Brandon Mull, Gavin Brown, Nick Eliopulos, Billy Merrel, and Emily Seife
The Book of Shane (originally four e-books, later they were put together in one paperback book.) by Nick Eliopulos
Tales of the Fallen Beasts by Brandon Mull, Gavin Brown, Nick Eliopulos, Billy Merrel, and Emily Seife
Books by timeline
1. Tales of the Great Beasts - Set during the First Devourer War.
2. Tale of the Great Beast Ninani - Set after the First Devourer War when the Greencloaks discover the Nectar.
3. The Book of Shane (#1) - Set directly before Wild Born.
4. Wild Born
6. Blood Ties
7. Against the Tide
8. Rise and Fall
9. The Book of Shane (#2) - Set after Rise and Fall.
10. The Evertree
11. The Book of Shane (#3) - Set after The Evertree.
12. The Book of Shane (#4)
13. Tales of the Fallen Beasts - Set before Immortal Guardians
14. Immortal Guardians
15. Broken Ground
16. The Return
17. The Burning Tide
18. Heart of the Land
19. The Wildcat's Claw