Garth Nix books in order
36 books in the catalogue, about 240 hours of reading in all; the shortest takes 2 hours and the longest 18 hours.
3 series and 27 standalone books in the catalogue.
The Keys to the Kingdom
7 books 1 Mister Monday length not known
2 
Grim Tuesday 5.9 h 3 
Drowned Wednesday 7.3 h 4 
Sir Thursday 6.4 h 5 Lady Friday length not known
6 Superior Saturday length not known
7 Lord Sunday length not known
The Seventh Tower
6 books 1 
The Fall 3.6 h 2 
Castle 4.0 h 
Above the Veil 4.6 h 5 
Into Battle 4.0 h 6 
The Violet Keystone 4.3 h
The Fall 3.6 h 2 Castle 4.0 h 3 Aenir length not known
4 Above the Veil 4.6 h 5 Into Battle 4.0 h 6 The Violet Keystone 4.3 h Old Kingdom
5 books 1 Sabriel length not known
2 Lirael length not known
3 Abhorsen length not known
Across the Wall 7.0 h Goldenhand length not known
Standalone books
Ragwitch 7.3 h 
Sabriel 6.5 h 
Shade's Children 6.3 h 
The Calusari 1.8 h 
Aenir 4.3 h 
Lirael Daughter of the Clayr 9.5 h 
To Hold the Bridge 7.8 h 
Abhorsen 7.2 h 
Clariel 7.6 h 
Mister Monday 6.6 h 
The Abhorsen Chronicles 18.4 h 
Lady Friday 5.9 h 
Superior Saturday 5.3 h 
The Best Science Fiction and Fantasy of the Year, Volume Three 9.1 h 
The Dragon Book 8.2 h 
Lord Sunday 6.2 h 
Zombies Vs. Unicorns 7.9 h 
Teeth 8.6 h 
Troubletwisters 5.4 h 
The Monster 5.6 h 
Rags & Bones 6.8 h 
Blood Ties 4.1 h 
Fearful Symmetries 7.3 h 
Newt's Emerald 5.3 h 
Goldenhand 7.7 h 
The Left-Handed Booksellers of London 7.6 h 
Terciel and Elinor 8.5 h