I'm not really into reading manga. I've tried before, and it's just really hard to get into for me.
This series generally moves pretty fast, but I can understand if you're bored by reading the first 45-50 or so chapters which is what the first two seasons cover, then the next 10-15 are the two OVAs about the music club and Tenri.
The thing about the third season is that it skips quite a bit to get to the Goddesses arc, two or three arcs that could have made up a season on their own.