Margaret Peterson Haddix books in order
27 books in the catalogue, about 128 hours of reading in all; the shortest takes 2 hours and the longest 9 hours.
2 series and 21 standalone books in the catalogue.
Shadow Children
7 books Among the Hidden length not known
Among the Impostors 3.2 h Among the Betrayed length not known
4 
Among the Barons 3.3 h 5 
Among the Brave 4.2 h Among the Enemy length not known
Among the Free length not known
The Missing
4 books
Standalone books
Running Out of Time 3.5 h 
Don't You Dare Read This, Mrs. Dunphrey 2.3 h 
Among the Hidden 2.9 h 
Turnabout 4.1 h 
Among the Imposters 3.2 h 
Amongst the Betrayed 2.9 h 
Escape from Memory 4.8 h 
The House on the Gulf 3.7 h 
Among the Enemy 3.9 h 
Double Identity 4.0 h 
Among the Free 3.7 h 
Uprising 6.5 h 
Palace of Mirrors 5.5 h 
The Shadow Children 3.2 h 
Into the Gauntlet 5.7 h 
Sabotaged 7.0 h 
Always War 3.6 h 
Caught 6.5 h 
Risked 6.2 h 
Revealed 8.5 h 
The Strangers 7.7 h