I'm not sure if it's a widely popular book. It might be relatively unknown to the general public but could have a niche following among those interested in certain types of novels.
Sure did. The manga of Jibaku Shounen Hanako-kun has ended. It might have been due to the creators having told the story they wanted to tell or reaching a natural conclusion in the plot.
I don't have much specific information about it. It could be about a club in a classroom setting, given the 'kyoushitsu' which means classroom in Japanese. But that's just speculation.
There might be, but it's not easy to find. Sometimes, fan communities or certain websites might offer it for free temporarily. However, make sure to only access content from legitimate and authorized places.