http://www.sakevisual.com/realistair/index.html
FREE and very high quality, if on the short side because it was done for a contest. Not QUITE a visual novel – there’s some skills raising, and less branching choices, but it’s close enough to give you an idea.

http://hanakogames.com/fatal.shtml
Length worth the $10, I can assure you. Good writing, more strictly a visual novel – though you have to solve a few puzzles. Art is not half as good as Re:Alistair but the plot is much more engaging.

I also high suggest you look up Phoenix Wright. There’s an iPhone/iTouch port now available for $5! (a steal considering the DS version was $30, if memory serves me right).

All these are very good, and strike different tones, which I think will allow you to see the range of visual novels.

The appeal for me is the characters, artwork, and plot. Unfortunately, the only translated visual novels are all eroge and marketed towards boys. I prefer otome games – female centered, but they are simply not available except for one (Yojinbo). I get my fix from indie game designers like hanakogames. But they lack professionalism (voice actors, CGs, length), mostly due to cost. The situation reminds me of manga in old days, actually. People are so adamant there’s no market for women-targeted visual novels. I think no one can be sure until there’s a wide release.

They can be fun to play, I loved Pheonix Wright. It almost feels like watching a cartoon but at the same time gives you the feeling of reading a book… it’s interesting.