Simulator in Zero Knowledge Proofs I'm reading about Zero-Knowledge-Proofs, in particular the argument of building a Simulator in order to prove the zero-knowledge property.
As expected, there's something that doesn't click yet.

Since a simulator is using a transcript to 'fool' the verifier, I understand the idea that since the Simulator knows nothing but the transcript, then the verifier can't extract any knowledge besides the statement being challenged.

Now, this doesn't prove that the verifier is not extracting knowledge from the transcript. If the transcript per-se has the knowledge, woudn't be a problem?.

Thinking it differently, if a monkey randomly type a Calculus book... yes, the monkey knows nothing about calculus, but a reading verifier would get real knowledge by reading his work.

Am I missing something?
..then the verifier can't extract any knowledge besides the statement
  being challenged.


Please let me amend it to, since a proper transcript (an indistinguishable one) can be generated by a simulator having no secret input at all, then transcript value is questionable for any reasoning about secrets (an easy, non-formal wording). In particular, a Prover can claim did not run (was not a party to) a protocol.


  Now, this doesn't prove that the verifier is not extracting knowledge
  from the transcript.


Knowledge extractor algorithm is a requirement for another property, proof of knowledge.


  Thinking it differently, if a monkey randomly type a Calculus book...
  yes, the monkey knows nothing about calculus, but a reading verifier
  would get real knowledge by reading his work.


Simulator is required to be efficient (expected polynomial running time), and calculus book is too complex to fit that. I'd suggest a weather forecast instead, like yes/no for rain tomorrow.

Back to book, a fast (efficient) reader would get garbage most of the times, with no chance to distinguish the correct case (proper textbook) better than guess.