I also like long books, but short books are fine and i want a series that is kind of long, but not too long so i can have something to stick with for a while.
I thought "Color" was good, as was "Boy's Love". What I want to know is why both repliers here have advertisement links in their signatures? Not cool, kids.
I also recommend the Doki Doki novels, Fevered Kiss and Green Light. I thought they would be rather tame, but they're not, really, and the stories were captivating and well translated.