Chris Wooding:
Storm Thief
Malice
Poison
Broken Sky Trilogy (The Twilight War, Communion, The Citadel)
Marcus Sedgwick:
The Book of Dead Days/The Dark Flight Down (2-parter)
My Swordhand is Singing
The Foreshadowing
Floodland
Philip Pullman:
His Dark Materials Trilogy (Northen Lights, The Subtle Knife, The Amber Spyglass)
Sally Lockhart series (The Ruby in the Smoke, the Shadow in the North, The Tiger in the Well, The Tin Princess)
Neil Gaiman:
Coraline
The Graveyard Book
Melvin Burgess:
Junk
Bloodtide/Bloodsong (2-parter)
Sara's Face
David Almond:
Skellig
Kit's Wilderness
Clay
Heaven Eyes
The Fire-Eaters
Kevin Brooks:
Being
Black Rabbit Summer
The Road of the Dead
Garth Nix:
Old Kingdom trilogy (Sabriel, Lirael, Abhorsen)
Keys to the Kingdom series (Mister Monday, Grim Tuesday, Drowned Wednesday, Sir Thursday, Lady Friday, Superior Saturday, Lord Sunday)
Terry Pratchett:
The Colour of Magic (Discworld book 1)
Johnny Maxwell series (Only You Can Save Mankind, Johnny and the Dead, Johnny and the Bomb)
Nation
Brian Keaney:
Jacob's Ladder
The Hollow People
Oisin McGann:
Small-Minded Giants
Ancient Appetites
Robert Swindells:
Room 13/Inside the Worm (2-parter)
Abomination
The Thousand Eyes of Night
Blitzed
Timesnatch
Stone Cold
Anthony Horowitz:
Alex Rider series (1st book is Stormbreaker)
Diamond Brothers series (1st book is The Falcon's Malteser)
Cliff McNish:
Breathe: A Ghost Story
Angel
Silver Child Trilogy (The Silver Child, Silver City, Silver World)
Malorie Blackman:
The Stuff of Nightmares
Noughts and Crosses series (Noughts and Crosses, Knife Edge, Checkmate, Double Cross)
Tell Me No Lies
Hacker
Linda Newbury:
Set in Stone
The Shell House
Alan Gibbons:
Hells Underground trilogy (Scared to Death, The Demon Assassin, Renegade)
Legendeer trilogy (Shadow of the Minotaur, Vampyr Legion, Warriors of the Raven)
The Dark Beneath
Blood Pressure
Hold On
Young Bond series (Silverfin, Blood Fever, Double or Die, Hurricane Gold, By Royal Command) - Charlie Higson
Angel Blood - John Singleton
Triskellion - Will Peterson
The Hitchhiker's Guide to the Galaxy - Douglas Adams
The Dark is Rising Sequence - Susan Cooper
The Hunger Games - Suzanne Collins
Here Lies Arthur - Philip Reeve
The Rule of Claw - John Brindley
The Black Tattoo - Sam Enthoven
Sophie's World - Jostein Gaarder
Inkheart - Cornelia Funke
The Thief of Always - Clive Barker
Fearless - Tim Lott
The Declaration - Gemma Malley
Life of Pi - Yann Martel
The Storm Garden - Philip Gross
The Giant Under the Snow - John Gordon
Century - Sarah Singleton
The Book Thief - Markus Zusak
Beyond the Deepwoods (Edge Chronicles book 1) - Paul Stewart and Chris Riddell
Jack Flint and the Redthorn Sword - Joe Donnelly
The London Eye Mystery - Siobhan Dowd
Across the Nightingale Floor - Lian Hearn
Elsewhere - Gabrielle Zevin
Numbers - Rachel Ward
Montmorency - Eleanor Updale
Mirrorscape - Mike Wilks
Airborn/Skybreaker (2-parter) - Kenneth Oppel
Bunker 10 - J.A. Henderson
The Boy in the Striped Pyjamas - John Boyne
A lot of these I reckon you'll like. A couple are aimed for older teenagers - Melvin Burgess and Kevin Brooks in particular - but that's just because of more mature content and stuff. You should be able to handle them easily.
And don't be put off if some of them look 'girly'. Just because lots of girls read them doesn't mean they aren't good books, although this isn't the case with Twilight. Don't bother. Reading Twilight is like having a hangover - good while it lasts, but you'll regret it afterwards. Plus all your mates will make fun of you.
Enjoy.