Mercedes Lackey books in order
80 books in the catalogue, about 610 hours of reading in all; the shortest takes 3 hours and the longest 19 hours.
9 series and 50 standalone books in the catalogue.
Heralds of Valdemar
3 books
Elemental Masters
17 books 1 
The Fire Rose 7.9 h 2 
The Serpent's Shadow 6.8 h 
Phoenix and Ashes 8.1 h 5 
The Wizard of London 6.8 h 6 
Reserved for the Cat 6.2 h 7 
Unnatural Issue 6.8 h 8 
Home From the Sea 5.7 h 
From a High Tower 6.1 h 
A Scandal in Battersea 5.8 h
The Fire Rose 7.9 h 2 The Serpent's Shadow 6.8 h 3 The Gates of Sleep length not known
4 Phoenix and Ashes 8.1 h 5 The Wizard of London 6.8 h 6 Reserved for the Cat 6.2 h 7 Unnatural Issue 6.8 h 8 Home From the Sea 5.7 h 9 Steadfast length not known
10 Blood Red length not known
11 From a High Tower 6.1 h 12 A study in sable length not known
13 A Scandal in Battersea 5.8 h 14 The Bartered Brides length not known
15 The Case of the Spellbound Child length not known
16 Jolene length not known
17 The Silver Bullets of Annie Oakley length not known
The Last Herald-Mage
3 books
The Mage storms
3 books
Mage Winds
3 books
Mage Wars
2 books
Vows and Honor
3 books
The Obsidian Trilogy
3 books
The Dragon Jousters
2 books 1 
Joust 8.1 h
Joust 8.1 h 2 Alta length not known
Standalone books
Burning Water 5.8 h 
Children of the Night 5.9 h 
Knight of Ghosts and Shadows 3.3 h 
The Last Herald-Mage (Valdemar 16.7 h 
By the Sword 11.9 h 
The Elvenbane 7.6 h 
The Lark And The Wren 9.0 h 
Bedlam's Bard 11.3 h 
Born to Run 6.2 h 
The Ship Who Searched 5.7 h 
If I Pay Thee Not in Gold 7.3 h 
Sacred Ground 7.0 h 
Elvenblood 6.4 h 
Excalibur 8.7 h 
The Silver Gryphon 6.0 h 
Owlflight 5.9 h 
Oathblood 7.2 h 
Owlsight 7.1 h 
Owlknight 7.1 h 
The Black Swan 6.9 h 
Brightly Burning (Valdemar (Chronological) #18) 8.2 h 
Take a Thief 8.0 h 
Exile's Honor 7.9 h 
The Gates of Sleep 7.1 h 
Exile's Valor 7.8 h 
Exile's Valor (Heralds of Valdemar - Prequel #2) 7.4 h 
Sun in Glory and Other Tales of Valdemar 6.4 h 
This Rough Magic 15.3 h 
Alta 7.8 h 
The Fairy Godmother 7.9 h 
The Wizard of Karres 8.2 h 
One Good Knight 7.1 h 
Fortune's Fool 6.7 h 
Foundation 6.2 h 
Intrigues 6.6 h 
Beauty And The Werewolf 7.0 h 
Changes 6.0 h 
Redoubt 8.4 h 
Bastion 7.0 h 
Dragon's Teeth 9.9 h 
Music of Darkover 4.6 h 
Blood Red 5.7 h 
Closer to Home 6.7 h 
The Heralds of Valdemar Omnibus 12.3 h 
Closer to the Heart 6.8 h 
Hunter 7.1 h 
A Study in Sable 5.8 h 
Elite 6.8 h 
The Last Herald Mage 19.4 h 
Eye Spy 6.2 h