Well my 3yo will look at a expensive toy for not very long, but play with a box (as a train) for ages... my 18mo will also sit & look at books turning the pages for a long time, & some toys do hold his interest (like trains he can push along) but generally not so much interest in many toys.
To be honest, I think so many toys are over rated, we feel we have to have them but for 100's if not 1000's of years children survived with much less & if he can concentrate on books then honestly I think he is just bored with the toys... have you tried giving him some plastic cups to try & stack or just a container with things to pull out of ... I remember my elder son, who didn't crawl until 10.5mo used to sit with 2 baskets of toys & take things look at them breifly (not play though) & move them to the other basket...At the same age he sat looking at the same picture book (on his own for 40mins) & now he will sit & concentrate on things that interest him for a reasonable amount of time so I think it is more about the interest he has in the toys - just cos they are supposed to be exciting for children doesn't mean they are going to be KWIM See what he does with a plastic bowl & spoon etc