We've heard good reports of the [http://www.collinseducation.com/series/read-on Collins Read On series]. They are printed on pure white paper rather than the white non-reflective paper preferred by the British Dyslexia Association. This does allow for better illustrations which can help to keep a reluctant reader motivated.
Younger children - and particularly boys - may well benefit from [http://www.oup.com/oxed/primary/projectx/ Project X].