The Replacement, by Brenna Yovanoff

Underneath the town of Gentry lies something evil. Something spoken of in whispers, if spoken of at all. It calls itself Mayhem, and it's citizens are a nightmarish collection of beings, some of whom can pass as human if you don't look too closely.

Mackie Doyle lives in Gentry with a loving family - but Mackie is not what he appears to be. He is from Mayhem, traded as an infant into a human family so Mayhem could take the human baby as a sacrifice. Now at 16, Mayhem wants Mackie back. He is getting sick (Mayhem says dying) because the human environment is slowly poisoning him. Then another baby is taken, and the baby's sister, Tate, turns to Mackie for answers. Relations between Gentry and Mayhem are strained and tense as Mackie finds himself drawn against his will into the eerie world of Mayhem to find answers both he and Tate need.

The book is dark, the imagery straight out of nightmares, but Mackie is such a compelling, strange, and sweet hero that I stayed up half the night reading because I couldn't put this down. This is imaginative and creepy at the same time - not for every reader.

Ingo, by Helen Dunmore

Ingo is a mysterious undersea world only found in old legends - until Sapphire and her brother Connor are called into that world from their ocean side home in Cornwall, England. But the mer folk that inhabit Ingo are not human, and their world is filled with danger for two human teens. Sapphire and Connor find themselves caught between two worlds in the opening book of this series.
The lure of the sea is as real as the tide, and the writing is hypnotic in this romantic adventure series.

Flash burnout, by L.K. Madigan

Blake's favorite subject is photography, and at 15 Blake can hardly keep up with the changes in his life fast enough to get a snapshot. He is negotiating new territory romantically with his girlfriend Shannon. Meanwhile, a photography class project sends him into the city, where he takes a photo of a passed out street person. Back in photography class, his photograph hits like a bombshell when his friend Marissa recognizes the picture as her meth addict mother. Marissa's vulnerability is exposed, and Blake protects her as a true friend. But life with 2 important girls is complicated, and Blake is headed for a crash course in girl trouble.

I liked Blake, the class comedian with girl trouble. I liked his older brother Garrett too, who for all his upperclassman cool, is there for Blake in the crunch. And then there is his Einstein look-alike Dad, the medical examiner who leaves autopsy tools on the kitchen table. And don't leave out his hospital chaplain mother who flies around the kitchen in hot-flash induced states of undress. But mostly it's Blake's memorable voice that the reader will remember - funny and confused and real, trying to do the right thing and bungling it all.