When you say that an event was a barnburner, what you mean is that it was excellent or very exciting. In other words, something that is a barnburner arouses a great deal of interest.
Examples: “I thought that the match between Federer and Nadal would be a barnburner. I was thoroughly disappointed.” * “When India and Pakistan play an ODI, it’s always a barnburner.” * Many of the commentators said World Cup final was a barnburner.
The expression `barnburner’ is mostly used in informal contexts.