I've read a bunch of alternate world books lately, which has been fun:
TANDEM, by Anna Jarzab. Two parallel worlds, one ours, one an alternate version of North America. The princess has disappeared (been taken by terrorists) and they're trying to hide that fact. So a guy gets sent to our world to bring her analog back to play the princess, just for a week until things settle down with a neighboring enemy nation. So, scifi thriller intrigue.
THROUGH TO YOU, Emily Hainsworth. Cam's girlfriend Nina was killed in an accident, and Cam's a mess without her. But then he finds a way through to an alternate world at the site of the accident--and in that world, Viv is alive. But things aren't *exactly* as they seem, as a girl named Nina, a friend of that world Cam but unknown to him in our world, is trying to tell him.
CRACKS IN THE KINGDOM, Jaclyn Moriarty (sequel to A CORNER OF WHITE). Probably my favorite of the group, but very strange. The first book is sort of slow at the beginning, and then suddenly you realize you're hooked. And the second book keeps on in the same strange but captivating way. In this one, there's the Kingdom of Cello, where a well liked farm boy named Elliot Baranski lives, and there's the World, where Madeleine Tully lives in Cambridge, England. Both have missing fathers (his to terrorists, hers to alcoholism). They find a crack between the worlds accidentally and start exchanging letters. So there's a large epistolary element to it. But then (hm, how to not spoil book 1??) Elliot needs Madeleine's help to find some people lost in the World who belong in Cello. If you are tired of dystopia or just want to cleanse the palate for a few hundred pages, this is a good antidote--it's sort of the exact opposite, while still having some scifi elements.
And then these two that aren't parallel world books, but are still scifi:
AVALON, Mindee Arnett. Bermuda triangles in space. Rogue scientists. Government conspiracies. And fast space ships. Fun.

TESLA'S ATTIC, Neal Shusterman and Eric Elfman. I have a low tolerance level for overly! quirky! middle grade! Love fantasy, but it's definitely possible to over-quirk your characters in any genre. So I really liked this one because it has just enough quirk and doesn't go overboard. Nick and his family move into their great aunt's house and the attic is full of junk--so they have a garage sale and get rid of it all. Only...it's not actually junk. It all DOES stuff--cool, strange stuff--and it turns out it was invented by Nikola Tesla himself. But bad guys--the Accelerati--are after it all, and Nick and his friends have to outwit them.