The cat was walking in the park. (simple) The cat noticed a hot dog stand, so he went over to get one. (compound) After he finished the hotdog, he went to go get some flowers. (complex) Though the pink flowers were pretty, the cat got the yellow ones, and he was very happy with his decision. (compound-complex)
The rain poured heavily. (simple) I was upset all morning, and I tried looking on the bright side; however, that's hard to do when there is not a bright side. (compound complex) Because of my upset, my father and I got to the train station late and had to wait an hour for the next arrival. (compound) I'm going to miss my grandfather, and I wish I had more time to spend with him. (complex)
Answer: Neutral tone is acceptable when writing about novels, but it is preferred to have an interesting tone to keep the reader engaged and interested in the essay.