I am thinking middle school aged, or possibly more for younger kids who read at a higher level. My daughter just finished kindergarten but reads at a 3rd grade level (no idea where she got that from, ha ha ha) and it is hard to find age appropriate subject matter that is at a challenging reading level! I would love to put out a series for kids like her!
P.S. Autumn thinks this is a fabulous idea and has decided that the cover should feature pictures of her - she even drew a cover for me. I think I am going to have to work on this for her!