Summaries from goodreads.

Here's a great website about the book series : Roswell High

The Outsider

He's not like other guys. Liz has seen him around. It's hard to miss Max -- the tall, blond, blue-eyed senior standsout in her high-school crowd. So why is he such a loner? Max is in love with Liz. He loves the way her eyes light up when she laughs. And the way her long, black hair moves when she turns her head. Most of all, he loves to imagine what it would be like to kiss her. But Max knows he can't get too close. He can't let her discover the truth about who he is. Or really, what he is.... Because the truth could kill her.

The Wild One

Falling in love from the moment she first encounters Nikolas, Isabel is irresistibly drawn to the young man who knows her so well, but she becomes suspicious at how much he knows and his possible hidden agenda…

The Seeker

Circle of danger...
Maria: She hasn't told her firends about the strange glowing ring that she found. It seems to be giving her powers -- special abilities that let her enter a world she's been dying to experience. Here's her chance to learn what she longs to know: how Michael feels about her.

Michael: He feels all alone on Earth and he's searching for a place to belong. He didn't count on discovering someone to care about right here in Roswell. Now he's falling for his best friend. But what he doesn't know, and Maria doesn't realize, is that she's drawing danger to them all.…

The Watcher

Life will never be the same...
Max is dying. No one wants to believe it, but he knows it's true. And as the end grows closer, he can only think of one Who will protect Liz if he's not here?
Liz can't stand watching Max suffer. She's determined to find some way -- any way -- to save him. But the only way to help Max is to risk her own life. Is she willing to die for the one she loves?

The Intruder

Love...too late? 

Michael: He's being held in a secret compound. But he's concerned less for himself than his friends. Max. Maria. Liz. Alex. And Isabel. He's got to get out before he's forced to betray the Roswell residents whom Sheriff Valenti is dying to capture. And once Sheriff Valenti has the information he wants, he won't be needing Michael anymore. Isabel: She used to think of Michael as a brother. But now that he's been captured, she seems to be the only one able to hear his every thought, feel his every emotion, share his dreams. Could this special bond between them mean they're meant to be together? Time is running out for Isabel to know for sure…

The Stowaway

Trust betrayed... 

Michael: He's still having flashbacks of his escape from the underground compound. Only Cameron, the mysterious girl he met behind bars, seems to understand him -- and realize that the sheriff may be gone but an even more dangerous enemy is out there.... Cameron: She fell for Michael while in the compound...spying on him for Sheriff Valenti. Now she feels guilty, and wishes she could tell him the truth. But how can she be honest -- without losing Michael?

The Vanished

Gone for good?
Max is on a mission to save Alex, who is stranded on the home planet. Alex may be lost or wounded -- or worse. To get Alex back, Max knows he'll need one of the Stones of Midnight. If only he knew where to find one...
Liz understands that Max can't rest until he finds Alex. And she's been busy herself -- spending time with Roswell newcomer Adam. She's been having so much fun with Adam that Max is in danger...of being forgotten.

The Rebel

Michael's dreams of finding his family are threatened when his brother, Trevor, has questionable motives.

Blood brothers...

Michael has finally found the one thing he always yearned for -- family. When his brother Trevor arrives in Roswell, Michael will do anything to please him. But soon Trevor's loyalties come into question -- and Michael is caught in the cross fire.

Maria's little brother has disappeared and she knows the kidnappers are trying to get to her and her friends. Devastated and guilt-ridden, Maria turns to Michael for help. But will he be there for her, or has Michael himself become the enemy?

The Dark One

True love never dies.
Isabel has run away from home, and Max knows her life is in danger. He has to find her and save her, but time is ticking away.
Alex is back on Earth, and he's a changed man. He looks better, feels better, and is ready to live life to the fullest -- without Isabel Evans. Little does he know he's the only person that can help the ailing Isabel. Will Alex be able to put aside his pride and save the life of his former love?

The Salvation

The ultimate battle.

Max is out of control. He's lying to his friends, ignoring his family, and has even turned on Liz. Has Max completely lost his mind...or is Max not really Max at all?

Liz hasn't felt connected to Max in a long time -- not the way she used to be. She knows he isn't the guy she fell in love with. There's something else controlling him. Something sinister. Can Liz help Max break free before he's lost forever?