Although Mercedes Lackey has almost thirty different science fiction and fantasy series set in at least five different universes, she is best known for her fantasy books set in her Valdemar universe.
Valdemar is a kingdom in a world with magic and magical creatures, many of them intelligent. Most of her books set in this universe feature telepathic and empathic bonds between humans and magical creatures resembling wolves, birds and horses. Her books are set in different time periods of the world's history spanning over 3,000 years.
Mercedes Lackey has co-authored books with both new and established authors including Anne McCaffrey, Larry Dixon, Marion Zimmer Bradley, Piers Anthony, and James Mallory.
If you like the telepathic and emotional bonding between humans and intelligent creatures such as horses or dragons, take a look at these series.
If you liked her strong, usually optimistic, heroines who come into their own during the story (usually without the horrific past you'll find in most recent urban fantasy), consider these:
If you enjoyed Lackey's urban fantasy series starring Diana Tregarde (witch and Guardian) take a look at these:
If you enjoyed Lackey's interpretations and retellings of fairy tales, especially with some romance, take a look at these: