What was Karl book which written in prison?

You're likely thinking of "The Communist Manifesto" by Karl Marx and Friedrich Engels. While it wasn't written specifically in prison, it was written during a tumultuous period in Marx's life, when he was facing exile from Germany and experiencing significant financial hardship.

The writing of the Manifesto was spurred by the need for a succinct and clear articulation of the communist movement's goals and ideals. It was a crucial work in shaping the future of socialist and communist thought.

It's important to note:

* "The Communist Manifesto" was written in 1847, before Marx was ever imprisoned.

* "Das Kapital", Marx's most famous work, was written over several decades and only partially finished before his death. While not written in prison, Marx did experience financial hardship and political persecution during its writing.

If you have a specific work in mind, please provide more details, and I'd be happy to assist further!