The writers/producers of Lost were big fans of The Stand by Stephen King, which is my favorite book of all time. It doesn't have the time travel aspect, but you can clearly draw parallels between characters in Lost and characters in The Stand. It's not a horror genre book, but a book about possibilities -- what if a virus took out 99.5% of the population of the Earth? What would those who survived do? I've read it once a year since I was in my teens. It's a very long book but worth the time investment.
If you like time travel, Stephen King also has a newer book -- 11/22/63 -- that talks about time travel in relation to JFKs shooting. Again, not his horror genre. I think King is amazing when he's not doing horror. I didn't read this one but my son did and he really liked it.