Gayle Callen books in order
17 books in the catalogue, about 116 hours of reading in all; the shortest takes 6 hours and the longest 7 hours.
17 standalone books in the catalogue.
Standalone books
The Knight's Vow 7.0 h 
My Lady's Guardian 6.8 h 
His Betrothed 7.0 h 
Hot and Bothered 5.7 h 
His Bride 6.9 h 
His Scandal 6.9 h 
No Ordinary Groom 6.8 h 
The Beauty and the Spy 6.8 h 
A Woman's Innocence 6.9 h 
The Lord Next Door 7.0 h 
The Duke in Disguise 6.9 h 
The Viscount in Her Bedroom 6.8 h 
Never Dare a Duke 6.9 h 
Never Trust a Scoundrel 7.0 h 
Never Marry a Stranger 7.0 h 
In Pursuit of a Scandalous Lady 7.0 h 
The Wrong Bride 6.8 h