What you have learnt.

This sentence was written in a book.

This looks strange to me,why ?

1.There is know "?" mark at the end of sentence.

2.The sentence is introgative as I think,so verb should follow the question world "What".

I mean "What have you learnt?" is correct.

Please clear my doubt.

If it is correct, it could only be an answer, to a previous question:

'What do you want to know about life?'
'What you have learnt.'

Otherwise, you are correct, Hanuman-- it should be written as a question; or, it should be part of a larger sentence, such as 'What you have learnt may be very important, but it cannot help me'.