A formal, systematic essay or book on some subject is called a

http://en.wikipedia.org/wiki/Treatise

how does this answer what i put

Read the first paragraph of the article I posted.

A formal, systematic essay or book on some subject is called a treatise. A treatise is a comprehensive and detailed examination of a particular topic, often written by an expert in the field. It aims to provide a thorough analysis, interpretation, and explanation of the subject matter. Treatises are typically crafted with a logical structure, evidence-based arguments, and well-researched information to present a comprehensive overview of the topic. Whether in the form of an academic paper or a published book, treatises serve as valuable resources for in-depth understanding and scholarly discourse on various subjects.