Mystery
The Body of Evidence series by Christopher Golden - 10 books - start with BODY BAGS
Sci-Fi/Horror/Fantasy
Prowlers quartet by Christopher Golden - start with PROWLERS
The Hollow quartet by Christopher Golden and Ford Lytle Gilmore - start with HORSEMAN
The Fallen quartet by Thomas E. Sniegoski - start with THE FALLEN
The Uglies trilogy by Scott Westerfeld - start with UGLIES
The Midnighters trilogy by Scott Westerfeld - start with
The Keys To The Kingdom series by Garth Nix - start with MISTER MONDAY
Roswell High series by Melinda Metz - 10 books - start with THE OUTSIDER
Fingerprints series by Melinda Metz - 7 books - start with GIFTED TOUCH
The Gemma trilogy by Libba Bray - start with A GREAT AND TERRIBLE BEAUTY
Magic or Madness trilogy by Justine Larbalestier - start with MAGIC OR MADNESS
Buffy the Vampire Slayer series by various authors - too many to list - single titles do not necessarily have to be read in order, but there are some mini-series - don't miss out on THE GATEKEEPER TRILOGY by Christopher Golden and Nancy Holder
Angel series by various authors - same as above - try the BtVS/Angel crossover MONSTER ISLAND by Christopher Golden and Thomas E. Sniegoski
Fear Street by R.L. Stine - same as above - start with THE NEW GIRL
Drama
The Tillerman Cycle by Cynthia Voigt - 7 books - start with HOMECOMING
The Cyd Charisse trilogy by Rachel Cohn - start with GINGERBREAD
The Alice McKinley books by Phyllis Reynolds Naylor - 21 books so far - start with THE AGONY OF ALICE
The Love Bukowski series by Emily Franklin - 4 books so far - start with THE PRINCIPLES OF LOVE
Comedy
The Alice McLeod books by Susan Juby - 3 books so far - start with ALICE, I THINK
The Confessions of Georgia Nicolson series by Louise Rennison - 8 books so far - start with ANGUS, THONGS, AND FULL-FRONTAL SNOGGING
Related Booklist: Juvenile Series of the 80s and 90s