Ds is currently reading stage 5 of Oxford Reading Tree at school but can easily read stage 8 at home. 
I bought a few ORT for at home but I don't want to buy more as it is boring enough for him having to trudge through every single book available in each stage, without having to do those ones at home too (and I can no longer get ORT Read At Home books at these levels.)
I have hunted around the bookshops and library for a series that he could read at home without reading ORT but which follows a similar progression.
I am overwhelmed by the choice out there and wondered if anyone could recommend a series to keep him interested?