No, don't tip him or her over. Don't even dig in your pocket or purse for a few bucks. All we ask is a few moments of your time and as many kind words as you can spare.
When you read a book you like — one of mine or somebody else's — please show your appreciation with a favorable review on Amazon, Goodreads or the on-line forum of your choice.
Every author loves to see that readers have enjoyed what we do. On sites like Amazon, your approval can help spur the Amazon algorithm to give the book greater exposure. That means more sales and page-reads for the author. In other words more income.
Authors who don't have to scramble for every nickel and dime have more time to write. So if you post good reviews for the authors you like, you're helping to make sure the author will write another book.
FYI: I'm doing okay in the nickels-and-dimes department, but I still love to see good reviews for my books.