I read them all twice within a week and a half. I absolutely adored them. The second was my least favorite and the last was my most favorite. I absolutely fell in love with the 2 main characters. I will occasionally still pick them up and read my favorite parts again. But, they are totally 100% my style of book as far as the whole vampire thing goes.
As far as being too mature, I thought they were very tastfully done and appropriate for a young adult audience.