It's never too late to read to your kids

My 12yo is the youngest of 5. The novelty of all things parent wore off by the time he was born. The older children went to gym, swimming and various other clubs. They complained about going, they wanted to come home after school, play with their mates, their toys, watch TV etc not go to some club, have tea, fit in homework and do some reading before being forced to bed too early just cos I was tired.
So number 5 son didn't do any of the above, he's dyslexic, he struggles with reading, he prefers to play on his own, he's imaginative, creative and bloody messy. He pretty much decides when he goes to bed, within a time frame. He pretty much chooses what he wants to eat (was gluten freed for 7yrs due to medical and behavioural needs) and we attempt no more than 30 mins of homework on a school night (tbh there is little homework).
Granny bought him a book for Christmas 'gansta granny' by David Walliams. He wasn't going to read it, he ignored it and moved it from sight.
Three nights ago I asked him if we could read the book together. He said no. I asked him if I should read it to him. He replied 'if you want, but I'm off to bed now' so I read a chapter, he asked for another, he asked me what some words meant and why they just didn't say that'll the first place.
The second night he didn't go to bed till 10pm I told him I was too tired to read, he begged, he pleaded saying he didn't realise there were rules to reading. So I read to him and last night he said if he went to bed at 8.30pm could I read for half hour instead of just two chapters and he's lined up a doctor who book for me to read next.