There is no dispute between the two main pedigrees of Greek manuscripts as to what Jesus asked, exactly. He had just been asked what needed to be done to inherit eternal life. Jesus responded by asking the man,
“In the law what has been written?” immediately followed by,
“How readest thou?” (or, “How are you reading?” = same thing).
In lay-person’s terms that simply means that Jesus wanted the lawyer (who was well versed in the law) to answer his own question, before Jesus would respond. Jesus required the man to answer according to what was written in law, but he was not wanting him to recite like a parrot – he wanted to know how that man understood the law. How did HE ‘read it’, equals, How did HE understand it?
There were various Judaic schools of theology that did not read the law exactly the same. Some rabbis would have built up a following of students who would assiduously hang on their every word and their every interpretation of the law, and go on to quote the rabbi as their authority when promoting that school of teaching. Some ‘lines’ of authority could go back not just many decades but even a century or two. As this Catholic Encycopedia points out, in Jesus’ time:
“the popular theology of Hellenistic Judaism precisely regarded this
combination of decalogue and chief commandments as the most important
part of the law (Philo).” Encyclopedia of Theology, a Concise
Sacramentum Mundi edited by Karl Rahner, ‘Law – New Testament 1. The
position of Jesus in regard to the law’ p. 827.
But Jesus was not interested in that. When he was challenged to state where his authority to teach came from, he referred to God the Father, in heaven! But, back to Luke chapter 10.
The man responded to those two questions of Jesus without hesitation, apparently. He knew what Jesus was asking, so he did what all pious Jews of that era would do – refer to the Shema in Deuteronomy 6:5 and Leviticus 19:18. He quoted those two commandments. The man was therefore not really answering Jesus’ second question, only his first. Yes, his answer could be taken as agreeing with the Shema, so that he was reading it exactly as written, but the next two sentences in their conversation showed that he did not entirely agree with the spirit of the law.
When Jesus said he had answered correctly, and said to go and do that and he would live, verse 29 adds the key point; “But he wanted to justify himself, so he asked Jesus, ‘And who is my neighbour?’” This betrayed the school of interpretation that this man belonged to, showing that he ‘read’ the law in light of its particular interpretation – that Samaritans were not considered to be ‘neighbours’ of the Jews, for Jesus went on to give the parable of the good Samaritan, to shame such an interpretation (or, reading of) the law, the Shema.