As a homeschooling parent, I found the Harry Potter series to be very useful in getting my middle daughter's reading level up. We started out in "assisted reading" mode (she reads until she gets to a word she can't pronounce, I pronouce it for her and make sure she understands what it means) for a few pages per day. By the second book she was reading on her own
Same thing with my nephew. His readin showed marked improvement after we gave him the series as a birthday gift---and made an effort to assist him with the reading.