Documentation in Good Product Management
Question: "I took the liberty and had a peek into the evaluation version of the Blackblot Product Manager's Toolkit® (PMTK) which brings me to the question of - How much documentation would good product management have?"
According to the Blackblot PMTK Methodology™ the Business Case, Market Requirements Document (MRD) and Market Plan documents constitute the PMTK Core Documents and are the most important documents in Blackblot Product Manager's Toolkit® (PMTK).
The three PMTK core documents are the essence of product management and serve as a backbone to almost all other PMTK templates. So with regard to your question of "How much documentation would good product management have?" the answer is that good product management should at least have all three PMTK Core Documents, each of which is prepared extremely well. Additional PMTK documentation depends on the company and the product.
It should be noted that all PMTK templates and particularly the PMTK Core Documents were designed with the "Just-enough Documentation" notion in mind. The concept of "Just-enough Documentation" (aka "Good-enough Documentation") is a very general notion that strives to efficiently produce a sufficient amount of verbiage to clearly convey certain subject matter.
Accordingly, all PMTK templates are created in such a way that each document attempts to efficiently provide the necessary details – not too little and not too much. Furthermore, the number of template documents in PMTK is the proper amount of documents to provide full coverage to the product management domain.