Yes it does
Person A : 'I only bother to read important books'
Person B: 'How do you make that judgement? What are important books?'
Person A: 'I think only factual books about real things are important, I don't like fiction books'
Person B: 'Well I think fiction is important for teaching us about the human condition.'
It is correct English but it sounds wrong because it refers to an abstract situation. "What are important books?" - you are searching for a justification of the term 'important books'. An equivalent question is "Why are some books more essential than others?" You would probably only ask this of you are sceptical about the value of a book.
A much more likely question is: "WHICH are important books?" - you are searching for specific books that are considered important. An equivalent to this is "Which are the essential books?" You may ask this question when searching for advice on which books to read or purchase.
The translated sentence means, to expand it, "What are the characteristics shared by important books? For example, they may have influenced the course of political history or address human problems which every society in the world experiences. What/which are the important books? In my opinion, "Das Kapital" is important because it was translated into many languges and the ideas propounded in it affected most of the countries of the world in the twentieth century and "The Interpretation of Dreams" by Freud. I am just learning german and got the interpretation wrong at first but I assume the german sentence has the first meaning.
You would need to use 'which' instead of 'what' in your answer for it to be correct English. The equivalent German would then be 'Welche sind wichtige Bücher'.
The answer "What are important books?" is a strange question to ask, but is still correct. You are effectively asking someone to explain the concept of an 'important book' as opposed to an 'unimportant book'.
English always has a conjugated verb early in the sentence.
English never puts the only verb at the end of the sentence.
For example, "Where is he going?" has a conjugated auxillary verb (is) at the beginning of the sentence, and a verb in participle form (going) at the end of the sentence.
Much more here: https://www.englishclub.com/grammar/questions.htm