It depends on whether I am enjoying the book or not. If Iike what i'm reading then I will read it properly; if I don't. then I'll skim. It also depends on how much time I have; if I want to finish a section, but don't have enough time to reach it, then I'll skim.
Similar to Bryony and Jennifer, if I'm reading for pleasure and enjoying it, then no I couldn't skim. In fact sometimes I worry that I've missed something and go back and read certain sections several times to make sure I've got every last nuance out of the text!
But when I was working or as a student or if a book now is boring me, then I'll skim until I get to a relevant part.
I honestly can't skim read. I've tried so hard to develop the skill, as it would have saved so much time through university, but I just want to absorb the meaning in every word and form them all together. Means I take so long to finish books!