Glass Mask is one of my all-time favourites. Surprisingly stupid I was to keep it at distance at first. With the plot, drawing style and long run I thought it would be a ginormous drag, but the contrast couldn't be much greater. From the first volume I was hooked. Somehow this manga claws itself onto you and doesn't let go.
Story:
The synopsis doesn't even slightly grasp the epic story Glass Mask is. It's all about dreams, love, talent, hope, friendship, family, tragedy and the ability to fight for what you want and never give up. Here we see a girl with no credit on whatever subject besides acting, in acting her soul lives and thrives. You get pulled in, rooting for Maya's dreams, Hayami's love, Ayumi's ambitions, Tsukikage's blissful afterlife. The never-ending plot-twists, plays, adventures, hurdles and accomplishments keep you interested and not once did I lose my patience (which for me is rare).
Art:
I still prefer modern-drawings more, but so far I haven't been truly bothered by it. The catch is that the artist doesn't really improve with time, in my humble opinion.
Long-run:
This story never bores me and despite running for so long it still feels so short. I can't wait till they bring out some more scanlations (I'm at vol. 38)
For other matters such as character development and story development, I can say they are prominent, Maya grows stronger and stronger, and not only in her acting skills.
To conclude: Glass no Kamen is a classic and must-read for shoujo fans, it manages to stay fresh and exciting even after 38 volumes.
(ps. For those who have read Ashita no Ousama, Skip Beat!, The One, Ingenuo and Paradise City, I highly recommend this. It has somewhat the same feeling at points, plus it revolves around a career/talented orientated (showbiz) plot too.)