 The series is noted for its diverse and believable non @-@ humanoid alien life forms , and for its pacifist philosophy . White chose the hospital setting as a way to generate dramatic tension without violence , and because in his youth he wanted to be a doctor but had to go to work . Some commentators have praised the whole series , while others have thought there was a decline after the sixth book . One reviewer described the last book as " in a very positive way , a throwback to an earlier era in science fiction " . 
