Yep, it's a two-edged sword. We have a style tweak for that in KOReader, so you at least get to choose it on a per-document basis, but it's still *very* broad when you apply it

.
It's split in two, margin/padding, and essentially looks like that:
Code:
p, li { margin-top: 0 !important; margin-bottom: 0 !important; }
Code:
p, li { padding-top: 0 !important; padding-bottom: 0 !important; }