http://en.wikipedia.org/wiki/Incest_...ure#Literature
Never read Flowers in the Attic, but I have read Heinlein's "Time Enough For Love" and I'm pretty sure at least one of Lumley's Necroscope books had an aunt/nephew scene. Not my cup of tea but it seems Amazon is getting a little thin-skinned in general.
Meh. Come the revolution...