NoNewTaleToTell: So I'm playing Soul Gambler, it's my first "visual novel" type game (unless Long Live The Queen counts) and it's actually pretty entertaining. I guess it could be described better as a "choose your own adventure" game, but the difference between that and visual novels seems a bit blurry, at least to me as a outsider to those genres.
The difference is... there is no difference.
I'm no VN expert, having only "played" Tsukihime and Fate Stay/Night. But both of them are very heavy on the novel part and have no gameplay whatsoever. It's basically reading and making some choices at pre-selected points in the narrative which give you different endings, and storylines. Although since some of the choices only open
after the first playthrough, the first time you play you will be railroaded towards a particular ending.
I've also played some Monster Girl Quest (don't ask) which had an extremely simplistic battle system. But that could be considered a sort of gameplay.