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In the Sci Fi aisle:

Simon R. Green
Partly a parody of the 1950s space-opera genre, the Deathstalker novels are also a satirical take on dictatorship, fascism, fashion, established religion and the media.   The series spans over 200 years of Green's fictional universe, and is known for its flamboyant style of narrative.  There is a large cast of supporting characters who are given as much depth as the hero.

Glen Cook
The Garrett P.I. series is a combination fantasy and mystery series about Garrett, a freelance private investigator. 

His other series is The Black Company. a gritty fantasy series that follows an elite mercenary unit through several decades of their history.  This is a cult classic among soldiers because they are depicted like real soldiers just doing their job.

David Weber
His novels range from epic fantasy (Oath of Swords, The War God's Own) to space opera (Path of the Fury, The Armageddon Inheritance) to alternate histoy (1632 series with Eric Flint) to military science fiction with in-depth characterization.    Many of his military stories feature female leading characters in what have previously been seen as traditionally male roles.  By doing this, he has explored the challenges faced by women in the military and politics. In his writing he creates a consistent and rationally explained technology and society.

Raymond Feist
Most of Feist's works are part of The Riftwar Cycle, a fictional universe featuring the worlds of Midkemia and Kelewan.  Human magicians and other creatures on the two planets are able to create "rifts" through dimensionless space that can connect planets in different solar systems.

In the Paranormal aisle:
Kelley Armstrong
In the Otherworld, the author superimposes supernatural characters upon a backdrop of contemporary North American life, with strong romantic elements. While it has overarching conflicts and plotlines is not an epic battle between good and evil.

Kim Harrison
The Rachel Morgan urban fantasy series set in an alternate history where a worldwide pandemic caused by genetically modified tomatoes led to the death of a large portion of the world's human population. At that point, the hidden "Inderlanders," creatures such as witches, werewolves, vampires, and more, came forward and revealed their existence to the world.

Rachel Caine
Joanne Baldwin is a Weather Warden, part of an organization that rents space from the UN. Their mission is supposed to be alleviating natural disasters before millions of people die.   Supernatural beings partner with Wardens to do their work.  Joanne's life complication is that she learns a lot of truths people don't want her to know.

Patricia Briggs
Mercedes (Mercy) Thompson, a Native American shapeshifter was raised by Werewolves.   Mercy, a VW mechanic by trade, learns her true nature and is caught up in the affairs of the local werewolf pack, led by Adam, the Alpha who lives next door, and the local vampire seethe, a member of which she has befriended.  The series is set in the Tri-Cities area of Washington state in an alternate world in which Werewolves and certain types of the fae have been forced to reveal themselves to the public.  Briggs is known for her lifelike characters and humorous dialogue-  

Anne Bishop 
Her critically-acclaimed Black Jewels Trilogy is the saga of a young but still-innocent Queen more powerful than even the High Lord of Hell-and the three sworn enemies determined to win her and gain a prize that could be terrible beyond imagining...

Charlaine Harris  
The wildly popular Sookie Stackhouse series is a first-person account of Sookie's life as a barmaid and telepath in the town of Bon Temps, Louisiana.   She has several other series that range from paranormal to cozies,

Maryjanice Davidson
The main character in the Undead Series is Elizabeth "Betsy" Taylor who turns thirty in the most unfortunate manner possible: she is laid off from work and then run down by an SUV.   Waking up in the morgue fails to improve her mood, and when she discovers she can't kill herself, she gets downright stroppy.  Being proclaimed "Queen of the Vampires" by the obnoxious Eric Sinclair, who places himself first in line to be her consort, proves to be the last straw.

Keri Arthur 
This Australian author is best known for a series of books revolving around the character Riley Jensen, who is a rare hybrid of vampire and werewolf and has a twin brother named Rhoan. Jensen works for an organisation in Melbourne called the Directorate of Other Races, which was created to police supernatural races.

Sherrilyn Kenyon
Her most popular series, The Dark-Hunters,  is about immortal warriors who sell their souls to the Greek goddess Artemis for one single act of vengeance against those who may have facilitated their death.   Afterward they are bound to protect mankind from Daimons; vampires who survive by taking human souls. Daimons are former Apollites, creatures cursed by the god Apollo for the murder of his mistress and son. Apollites cannot go in the sun, must feed off of each other to live, and are destined to die on their 27th birthday if they choose not to become daimons.

Richelle Mead  
The Georgina Kincaid series, is a first-person perspective of a Succubus working at a local book store.  A succubus is a demon who takes the form of a woman to seduce men in dreams.  

Laurell K. Hamilton      
Her Anita Blake series features a female necromancer turned magical investigator.   Her other popular series is the Merry Gentry series which is an urban fantasy in which the world of fairy interacts with the "real world".

Carrie Vaughn
Kitty Norville is a werewolf who hosts a popular syndicated radio phone-in show based in Denver called "The Midnight Hour". The program focuses on supernatural issues.

Rachel Vincent
The Shifters series is a present-day urban fantasy series about a female werecat.