If you are a friend of a writer, write reviews for the author wherever possible. Remember how you like to know about the book from a reader before you purchase it? If you like a book and you write a good review, you will help the author reach a bigger audience and help his book to sell. Most of us writers don't make money on our writing, but our hope is that people will read our work and appreciate what we do.
Recently several people wrote reviews for me here. It is easy. Just click on the line that says
comments. Usually a number precedes the word.