Here's a list of the series I'm reading, by author

Ann Brashares
Sisterhood of the Travelling Pants series
The Sisterhood of the Travelling Pants
The Second Summer of the Sisterhood
Girls in Pants: The Third Summer of the Sisterhood
Forever in Blue: The Fourth Summer of the Sisterhood

Meg Cabot
The Queen of Babble series
The Queen of Babble
Queen of Babble in the Big City
Queen of Babble Gets Hitched
The Princess Diaries series
The Princess Diaries
Princess in the Spotlight
Princess in Love

Orson Scott Card
Ender's Saga
Ender's Game
Speaker for the Dead
Children of the Mind
A War of Gifts
Ender in Exile
plus: Ender's Shadow

Ally Carter
Gallagher Girls series
I'd Tell You I Love You, But Then I'd Have to Kill You
Cross my Heart and Hope to Spy

Suzanne Collins
The Hunger Games trilogy - done
The Hunger Games
Catching Fire

MaryJanice Davidson
Queen Betsy series
Undead and Unwed
Undead and Unemployed
Undead and Unappreciated
Undead and Unretumable
Undead and Unpopular
Undead and Uneasy
Undead and Unworthy
Undead and Unwelcome
Undead and Unfinished

Anne George
The Southern Sisters series
Murder on a Girls' Night Out
Murder on a Bad Hair Day
Murder Runs in the Family
Murder Makes Waves

Sue Grafton
Alphabet series
A is for Alibi
B is for Burglar
C is for Corpse

Jackie Kessler
Hell on Earth series
Hell's Belles
The Road to Hell

Laurie R. King
Mary Russell series
The Beekeeper's Apprentice
A Monstrous Regiment of Women
A Letter of Mary

Sophie Kinsella
Shopaholic series
Confessions of a Shopaholic
Shopaholic Takes Manhattan
Shopaholic Ties the Knot
Shopaholic and Sister
Shopaholic and Baby
Mini Shopaholic

Dean Koontz
Odd Thomas series
Odd Thomas
Forever Odd
Brother Odd
Odd Hours

Henning Mankell
Kurt Wallander series
Faceless Killers
The Dogs of Riga
The White Lioness

Melissa Marr
Wicked Lovely series
Wicked Lovely
Ink Exchange
Fragile Eternity
Radiant Shadows

Ann M. Martin
The Babysitters' Club
Kristy's Great Idea
Claudia and the Phantom Phone Calls
The Truth About Stacey
Mary Anne Saves the Day
Dawn and the Impossible Three
Kristy's Big Day
Claudia and Mean Janine
Boy-Crazy Stacey
The Ghost at Dawn's House

Alexander McCall Smith
No. 1 Ladies' Detective Agency series
The No. 1 Ladies' Detective Agency
Tears of the Giraffe
Morality for Beautiful Girls
The Kalahari Typing School for Men
The Full Cupboard of Life
In the Company of Cheerful Ladies
Blue Shoes and Happiness
The Good Husband of Zebra Drive
The Miracle at Speedy Motors
Tea Time for the Traditionally Built
The Double Comfort Safari Club

Stephanie Meyer
Twilight series
New Moon
Breaking Dawn

L.M. Montgomery
The Anne series
Anne of Green Gables
Anne of Avonlea
Anne of the Island
Anne of Windy Poplars
Anne's House of Dreams

Rick Riordan
Percy Jackson series
Percy Jackson and the Lightning Thief
Percy Jackson and the Sea of Monsters
Percy Jackson and the Titan's Curse
Percy Jackson and the Battle of the Labyrinth
Percy Jackson and the Last Olympian

Lemony Snicket
A Series of Unfortunate Events
The Bad Beginning
The Reptile Room
The Wide Window

Joss Whedon, et al.
Buffy Season 8 series
Long Way Home
No Future for You
Wolves at the Gate
Time of Your Life
Predators and Prey
Buffy Omnibus
Buffy Omnibus, vol. 1
Buffy Omnibus, vol. 2

Laura Ingalls Wilder
Little House on the Prairie series
Little House in the Big Woods
Little House on the Prairie
Farmer Boy
On the Banks of Plum Creek

Bill Willingham
Fables Volume 1 - Legends in Exile
Fables Volume 2 - Animal Farm
Fables Volume 3 - Storybook Love
Fables Volume 4 - March of the Wooden Soldiers