I think, this series show why teenagers or not mentally adult people shouldn't play with sex. And that sex isn't way to show or perceive a love. It can be fun but it's not enough to fill the heart's content.
But for those who can understand this moral there not necessity to read Girlfriend.
Though, even if it has few sweet moments, mostly it was sad for me to read.
It's a shame that parents wasn't guide their children through puberty and didn't explain them what real the love is. So that children was pushed on the painful way of raising experience by method of efforts and mistakes. And yes, they got experience, some of them understood their feelings but... they never could again start relationship with someone as pure, innocent human being....