I must totally recommend the Japanese Graded Readers series by White Rabbit.
I really needed some practice reading to reinforce what I've learnt so far (almost 4 months now), and I wasn't sure about manga or any other text. I wasn't very fond of reading children books, specially to keep me motivated.
This series presents graded material (from level 0, wich it's perfect for me now) with topics and stories that aren't necessarily childish, so I really enjoy reading it, and I get a real confident booster whener I finish a story.
A bit pricey, but otherwise totally recommended!