1 Everworld, by K.A. Applegate
This was technically the first two books of the Everworld series. Basically, the main character, David, is new in town, and he starts dating this girl Senna. Then one morning, he and a few other students from school end up over at the park. They see Senna sitting on a rock, then suddenly a whole rips open in space and a giant wolf comes through and grabs Senna. The others, David, April, Jalil, and another guy whose name I can't remember, start running after her as the wolf retreats back through the hole in space, and they somehow end up going through the portal with them and find themselves in Everworld, a place all the gods- Norse, Egyption, Aztec, etc.- created to be their own world, so that all these different people groups live there and serve their gods and pillage each other and stuff. Obviously, it's much different from the present-day. Senna is nowhere to be found, so these four high schoolers have to try to find her and figure out how to get home. But there's another twist. While they're trying to survive and not get killed in battle/sacrificed to the Aztec god of the sun (Huitzilopoctli or something?)/caught by Loki, they are also living their lives back in the regular world. Another version of them goes about their everyday lives, and when they fall asleep in Everworld they return to the regular world. So that's strange. But they can't figure out how return permanantly, so every time they wake up they're back on a viking ship or hiding out in the woods or wherever they happened to be in Everworld. So that's that in a nutshell. It was an interesting book, but I don't think I'm going to read any more of the series. It was extremely confusing before the author explained a little more about what was going on, and two books in I still don't completely understand what's up. But that's not really a problem- I have plenty of other books to be reading, anyway :P
2. Endymion Spring, by Matthew Skelton
Endymion Spring switches back and forth between two different times/places/characters throughout the story. You start off in Mainz (Germany? Austria?) in 1453 or so, from the perspective of Endymion Spring, the young mute apprentice of Johann Gutenberg, who's in the process of inventing the printing press. The two are approached by Johann Fust, who you can see from the beginning is up to no good. He offers to back Gutenberg's plan and give him the gold to get his project going and start work on the Gutenberg Bible if he is will just allow him to use his printing press when he wants to. Fust brings with him an ominous-looking chest. Inside? Paper. But not just any kind of paper. This is special. It contains within it the secrets of the universe, if only Fust could unlock them. And that's why he's really there. He thinks Endymion is the key to seeing inside this magical paper. Endymion, young and intrigued, foolishly falls right into Fust's trap, but quickly realizes his mistake and sets out to hide the paper from Fust and prevent him from using this knowledge for evil. Meanwhile, in present-day Oxford, young Blake Winters stumbles upon a book, called Endymion Spring, in one of the libraries. Though it appears blank at first, the pages reveal riddles and writings that only Blake can see. It quickly becomes apparent that there is something special about this book, and that Blake is not the only one who knows about it. Can he unlock its mysteries while still keeping it safe from the Person in Shadow? This book started off kind of slowly for me, and I'm pretty sure it's meant to be read by, like, Middle Schoolers. But it got a lot more interesting later on, though there were still some minor details and plotpoints that I don't feel were explained properly.
So, yeah! Those are the books I've read so far. Be looking out for the next thing I finish! I haven't decided what to read next yet... But I'll figure it out! See ya!