I would recommend Divergent too, the third in the trilogy is being released later this year so not too long to wait if she enjoys the first two.. I thoroughly enjoyed the first books, as did my teenage son and now my 11 year old daughter is reading them and also enjoying them.
Your son did brilliantly, one of my sons friends was diagnosed with dyslexia in Year 6 (now Year 9) and he gets all sorts of help and extra time in tests, so to achieve what he did without that help is fantastic..