There's never really anything I habitually return to, I am pretty much just always reading some different sci-fi of some kind. Currently working on the Zones of Thought trilogy by Vernor Vinge. I finished the first book and was so absolutely ready to plow straight into the second book and follow the same characters and alien species through some new crazy adventure, but was met with a completely different set of characters and completely different aliens, which was a bit surprising. Still enjoying it, though!