Yes Guest Books are essential. They help you gain valuable feedback from your guests like hints and tips of places to visit. We have guest books but also take feedback via online booking sites.
It doesn't only help the property owner it's also a useful source for new guests to visit the property. It's nice reading the book, as they now stretch back over 10 years of rentals. Guests can read about the many adventures and experiences that previous guests have had.
A hardback guest book can also be a nice feature on a coffee or side table.