Further note: I'm going to ask a professional English tutor about the question you have raised. I would like to know the exact answer, anyway! I'll come back to you.
Sincerely,
mjm

Thank you very much for taking my questions so seriously. I admire your rigorous scholarship. Based on your explanations, I'd like to tell you my understanding.
"I enjoyed hearing you talk about books..."
In this sentence, "enjoyed" is a verb, "hear you talk about books..." should be a noun clause as an object. As another commentator said before, "talk about" in this sentence should be "to talk about". It's a verb infinitive, but the "to" is omitted. I think your other expression is completely right: "I enjoyed the books when you talked about them". The sample sentence is an independent sentence, but your sentence is actually two sentences because it includes an adverbial clause of time, so in different sentence patterns the verb tenses should be changed accordingly. I think I already know the answer to this question. Thank you very much for giving me such detailed explanations.

Sincerely,
Jack

You are welcome, Jack! Just to say that I have received a response from my colleague, and she agrees with you and the previous commentator. Please just view my previous response as an unqualified skirting around the subject! I have been speaking English for around 50 years but I’m still learning!! Wishing you all the best with your studies. Sincerely, mjm

You are too modest Mjm. All your understanding of this question makes good sense and because of it, I got the point. I like your academic attitude, and that’s what I long for.

*主要动词是"enjoyed hearing"

Okay, I kind of see. Maybe it is because the word enjoyed already indicated tense. Thank you very much.

Yes it's like when you say:
I want you to come
I will want you to come
I wanted you to come
"To come" is a complement verb dependent on the main verb "want"
Only the latter indicates the tense