Writers are a pretty self-conscious bunch. We work for hours day in and day out, sacrificing so much, and never really know if what we're doing is worth it. Is it good or just crap? The only way to know if the stories in our head come out on paper (or e-reader) as vividly as we hope is to get feedback from readers. The best way to thank an author for a story you read and enjoyed is a review, whether it be on Amazon, Goodreads, email, blog post, FB post.
Recently my husband passed my debut novel, the only one in print, on to a coworker. Two days later he came home with this note:
I loved your book! You are an amazing (with the word "amazing" underlined TWICE!) writer. I read it in a day and a half. Can't wait to read your next one and I loved the title. Continue writing...it's what you should be doing!!
This has to be the best review/letter I've ever received about my work. It really means the world to me!