What are some nice things to say to an author over a letter?

[Arifa C]

i've got this assignment to do about a book i read over the summer i have to write a letter and i'm stuck with concluding the letter. i thought it would be good if i ended it with some nice things to say but i just can't think of any.....this is a high school assignment so i need to make this good....thanx for everyone that answers this question