Could someone clarify the criteria for questions being too technical (or off-topic) for Books.SE?

Question

Proposal: Books

I am confused as to whether asking for a book or list of books about a specific (very) technical subject would be off-topic or inappropriate. First, it says in the description of the proposal (emphasis added):

About all kind of books, technical, programming/computer related, fiction, nonfiction, etc.

Second, the question Which is the best book I can find to learn project management? has been judged on-topic 7 to 1. But then another question, What is the best book to learn c#?, has almost evenly divided votes, 7 for not a good example and 6 for on-topic, with further two comments that state that the subject of the question is too technical and is better suited for StackOverflow.

So, my question is: which of the following subjects (taking into consideration the (un)availability of specialised stacks and their respective policies) would be appropriate for Books?

• Quantum field theory (text)books
• Linguistics 〃
• Quantum mechanics 〃
• Evolutionary biology 〃
• Cognitive psychology 〃
• History of wall art in Westminster in the 10th century CE 〃
• Thermal history of Mars as inferred from orbital geochemistry of volcanic provinces 〃

Answer 1

The issue isn't the topic; the issue is the phrasing of the proposed question.

From the FAQ:

Ask questions that can be answered.
Avoid asking questions that are subjective, argumentative, or require extended discussion. Stack Exchange does not work well with questions like "Which is the best…"

So if someone proposes "What are the best romance novels?" as a question, that should be voted as Not a Good Example—because that's explicitly listed as a type of question that shouldn't be asked on any SE site.