Hi
I have posted 'rants' on this topic before!
The majority of Reception children do not 'read' as such - yes, share books, look at pictures, talk about what the book might be about, etc.
Does DS know his sounds? Reading today should be using a phonics scheme, NOT the old whole words 'look and say' methods.
I have worked as Teaching Assistant for over 20 years, and am now a voluntary helper in a small Primary school, two days a week, mainly supporting five Reception children, but not much of what we do is 'reading'.
Perhaps ask his teacher exactly HOW he should be reading, and what is the best support you can give.
I stand to be corrected, but I would not expect a R child to have to do much more than just 'share' a book with someone at home.
What scheme books are they on? I hope it isn't Oxford Reading Tree, which if you have looked at many postings on here, is not rated very highly these days: 20 years ago, Yes, but not now (though they have introduced phonics books that some schools use - Songbirds I think it is called.)
If you need any further help, come back to me if you wish.