Another series that could be reprinted in wake of Pittacus Lore's I Am Number Four is a series that saw publication between 1997 and 1998 called Extreme Zone. This series was written by M.C. Sumner, kind of riding off of the success of The X-Files television show. It even has an eye in the cheesy logo, like the one in the opening credits for the show.
There were eight books in the series in all. The synopsis for book one, from the publisher:
"Noah Templer: Every night I wake screaming, drenched in a cold sweat, my heart racing. I remember glowing figures bending over me, cutting me open with alien instruments - but that's it. If I don't find out where these nightmares come from, I'll go insane...or am I already too far gone?
Kathleen 'Harley' Davisidaro: From the moment I arrived with my father at the Tulley Hills Research Facility, I didn't trust the people - or their top-secret project. Now my father's disappeared. And nobody will tell me where he went. They want to ship me off the base, but I'm not going anywhere - not until I find out the truth!
The moment Noah and Harley meet, they find an immediate connection - a connection that goes deeper than either ever could have believed. Alone, both are lost in their personal terrors of the night. Their last hope lies in learning to trust each other, but in the Extreme Zone, they can never trust anyone - including themselves..."
This series certainly capitalized on the government-conspiracy-paranoia stuff from The X-Files, but set in a high school, with a good amount of romance between the characters. I remember this series being pretty action-packed with aliens that were genuinely frightening to me at the time. It's more of a traditional abduction/cover-up tale than books about aliens that came later, like I Am Number Four, and even Roswell High, which debuted in 1998, but it's good scary stuff that could potentially be republished in the current market.