For me it varies; leisure reading can go from zero to 14 hours depending on the day of the week, the season, and whether there is a Bethesda RPG recently out.
(Or if I get dragged out to go--shudder--shopping.)
If I include web-surfing and reading emails then the range runs from 2 to 18 hours. It helps that I rarely need more than 6 hours sleep and I'm not a foodie.