Some students naturally pay more attention to details, as I am sure you know. Does he pay attention anywhere or is this a global tendency he has, not to be detailed?
In terms of the reading, I would make sure that the material is at or below his reading level, so when you ask for details, at first, it is easy for him to produce the needed details. Sometimes the lack of attention is due to the material being too difficult . (Not necessarily above his ability but perhaps above the level of effort he currently is motivated to put out). Also, pick readings of high interest. If he is competitive, try to compete with him a little on reading something and getting the details right.
The reasons we do the outlining in the earlier stages is precisely to get the students to pay attention to all the details. In literature, it is often the details that are important, the subtle stuff that hangs in the shade, not the blatantly obvious stuff.
If your student is more of a math or science minded person it is quite the opposite. In science we are often looking at the effect that is dominant and considering lesser effects negligible, so we are more so looking for the obvious (not always, but certainly at the K -12 level of science), so he may be conditioned to just thinking about things in a more scientific way.
I would definitely read with him, don’t leave him alone. Taking turns reading aloud is a great idea. After each paragraph or three, stop and note details, perhaps even compete to find the most details.
But, also, if you do try to motivate him to find details, please, also make a strong point of explaining why the details are important. What is it about the stuff that happens on the side that is important? One good place to go for that sort of detailed reading would be mystery books, like Sherlock Holmes or Agatha Christie. The main story line is almost always misleading because someone has reason to hide both his motivations and his actions. Every little observation Holmes makes is of great import.
Let me know if you have other questions.