Honestly, I cannot believe all the books that are on this list - and yet that's still not stopping me from buying more and downloading anything that sounds remotely interesting when it's a free e-book.
The Dark Unwinding Series by Sharon Cameron
Seraphina Series by Rachel Hartman
Clockwork Dagger Duology by Beth Cato
The Icarus Project Series by Jackie Kessler
Illusive Series by Emily Lloyd-Jones
Twelve Houses Series by Sharon Shinn
The Company Wars Series by C.J. Cherryh
The Mortal Instruments Series by Cassandra Clare
Sirantha Jax Series by Ann Aguirre
Petaybee Series by Anne McCaffery & Elizabeth Ann Scarborough
Farseer Trilogy by Robin Hobb
Age of Steam Series by Devon Monk
Lumatere Chronicles by Melina Marchetta
Earthsea Cycle by Ursula Le Guin
Song of the Lioness Series by Tamora Pierce
The Conspiracy of Us Series by Maggie Hall
Dragon Blood Series by Lindsay Buroker
The Sin Eater's Daughter Series by Melinda Salisbury
Chronoptika Series by Catherine Fisher
The Queen's Thief Series by Megan Whalen Turner
Secrets of the Zodiac Series by Elizabeth Cole
Mandrake Company by Ruby Lionsdrake
Code Name Verity Series by Elizabeth Wein
W.A.R.P. Series by Eoin Colfer
Maze Runner Series by James Dasher
Ancient Guardians Series by S.L. Morgan
Anniversary of the Veil Series by Vanna Smythe
Circle of Magic Series by Tamora Pierce
Crown & Court Duology by Sherwood Smith (I own both these)
Vampire Academy by Richelle Mead
Seven Realms Series by Cinda Williams Chima
Rogues of the Republic Series by Patrick Weeks
Leland Sisters Series by Marissa Doyle
Encrypted Duology by Lindsay Buroker
Norothian Cycle by Edward M. McNally
The Rys Chronicles by Tracy Falbe
Elei's Chronicles by Chrystalla Thoma
Touchstone Series by Andrea K. Host
Gryphon Series by Stacey Rourke
The Fury Triad Series by Patricia Burroughs
Chronicles of the Necromancer Series by Gail Z. Martin
The Nethergrim Series by Matthew Jobin
Princess Series by Jim C. Hines
Moonworlds Saga by Sean McMullen
The Looking Glass Wars Series by Frank Beddor
Wrapped Series by Jennifer Bradbury
The Drifting Isle Chronicles by Assorted Authors
Dark Matters Series Claire Robyns
Timbound Series by Rysa Walker
Once Upon A Curse Series by Kaitlyn Davis
The Wilderhark Tales Series by Danielle E. Shipley
The Twelve Kingdoms Series by Jeffe Kennedy
Whispers From Mirrowen by Jeff Wheeler
True Reign Series by Jennifer Anne Davis
His Fair Assassin Series by Robin LaFevers
The Artifactor Series by Honor Raconteor
The Belgariad Series by David Eddings
Confederation Series by Tanya Huff
The Culper Ring Series by Roseanna M. White
Summoner Series by Taran Matharu
The Keepers' Chronicle Series by Becky Wallace
Earth Girl Series by Janet Edwards