At the end of chapter 8, we read that the land was at rest. Chapter 9 was all sorts of upheaval as Abimelech tried to seize control of the land. At the end of chapter 9, Abimelech is killed and it seems like the land is at rest, even though we are not specifically told so.
Read verses 1-2: Tola judges Israel 23 years, then dies.
Read verses 3-5: Jair judges Israel 22 years, then dies.
Clearly not much information is given about these two men. They were judges for a number of years. Tola somehow saved Israel. Jair had sons with donkeys and cities. That's about all we know.
There are a few explanations for why this may be the case. They did nothing noteworthy (good, nor bad). Twelve is a popular number in the Bible, so they need to be mentioned so that we can have 12 judges. My guess is that they just lived during quiet, peaceful times (aka, the land was at rest). Think about it, if you are writing the history of the USA in 21 brief chapters, are you going to spend much time on James Garfield, Chester Arthur, Howard Taft, or Jimmy Carter? No, you'd focus on the guys at Mt. Rushmore (George Washington, Thomas Jefferson, Abraham Lincoln and Teddy Roosevelt), FDR or JFK. They are the guys who were presidents at significant times in our country's history. It's not that what other presidents did was insignificant, just not as noteworthy. Of course, I'd give Taft a verse or two mentioning about getting stuck in the White House bathtub or mention in a verse that Garfield was the first left-handed president.