I liked it too, but it used to be overhyped. And too American, maybe, it did feel different from other VNs for one reason or another.
Yume Miru Kusuri is the next logical choice as it's the one most similar to KS. You might also like Kira Kira if you want a high school romance, but Overdrive VNs are an acquired taste.
Type-Moon and Key VNs are classics, but as they are extremely long, pacing is an issue with their VN's. Tsukihime and Rewrite are my favorites, but people tend to like Fate/Stay Night and Clannad more.
What a Wonderful … Series is nice if you want artsy. Forest is if you want full-blown mindfuck. If you know Urobuchi, you'll recognize his style in Saya no Uta and Kikokugai- the Cyber Slayer.
Muv Luv and its sequel are arguably the most famous VNs. Muv Luv's meh, but it's worth reading through to get to the great real robot action of Alternative. If you want super robot action instead, Demonbane is fun.