Before the coffee gets cold, by Toshikazu Kawaguchi

 

This is a slight but charming book about a cafe in Japan where customers can travel though time. There are a lot of rules about time travel; you can only do it from one seat in the coffee shop, you can only do it once, you can't actually change history, you have to stay in your seat, and you can only stay as long as it takes to drink one cup of coffee. This book includes four interrelated vignettes that show how four people traveled through time to address regrets they have. I enjoyed the stories, although they would have benefited from some editing; there's a little too much repetition with each story including the set of rules. There are now five books in this series, attesting to its popularity; however, even though I enjoyed it, one was enough for me.