Diana Gabaldon books in order
25 books in the catalogue, about 300 hours of reading in all; the shortest takes 5 hours and the longest 24 hours.
1 series and 18 standalone books in the catalogue.
Outlander series
9 books 1 
Outlander 13.2 h 2 
Dragonfly in Amber 15.8 h 3 
Voyager 19.1 h 4 
Drums of Autumn 17.0 h 
A Breath of Snow and Ashes 24.1 h 7 
An Echo in the Bone 15.3 h 
Go Tell the Bees That I Am Gone 17.0 h
Outlander 13.2 h 2 Dragonfly in Amber 15.8 h 3 Voyager 19.1 h 4 Drums of Autumn 17.0 h 5 The Fiery Cross length not known
6 A Breath of Snow and Ashes 24.1 h 7 An Echo in the Bone 15.3 h 8 Written in My Own Heart's Blood length not known
9 Go Tell the Bees That I Am Gone 17.0 h Standalone books
Forastera 12.2 h 
The Fiery Cross 18.2 h 
Excalibur 8.7 h 
The Outlandish Companion 11.2 h 
Lord John and the Private Matter 5.6 h 
Lord John and the Brotherhood of the Blade 9.4 h 
Lord John and the Hand of Devils 5.9 h 
Written In My Own Heart's Blood (2 editions) 15.8 h 
The Dragon Book 8.2 h 
Songs of Love & Death 11.9 h 
Warriors 13.5 h 
Down These Strange Streets 9.1 h 
No Rest for the Dead 5.3 h 
A Trail of Fire 6.2 h 
The Scottish Prisoner 10.3 h 
Dangerous Women 14.4 h 
Virgins 4.7 h 
MatchUp 8.5 h