Chrisjen is light on description, as are most of the details in The Expanse books. The dialogue does all the heavy lifting, which ends up being a decent tool through which to visualize people as it allows your imagination to fill in the details. The things that we do know about her are that she's 1) a skinny and short grandmother, 2) she's Indian by decent, and 3) she swears like a sailor (preferring the "f" bomb to just about any other swear word). You kind of need to get used to seeing it on the page in any chapter that you read.
Chrisjen starts out as the Deputy Undersecretary of the United Nations, which is the second most powerful position on Earth. This was a decent starting point for this character and made it so that she could ascend to Secretary-General of the United Nations in Nemesis Games after Earth is destroyed by rocks hurled by belter terrorists from outer space. An Artist by the name of TenshiRisu visualized Chrisjen Avasarala as looking like this picture (inset above and to the right). I don't think that the artist did a very good job of nailing the character. For one, Chrisjen is always described as wearing these bold and beautiful sari's. Second, she's always eating pistachio nuts, so there should have been something along those lines in the picture. If you are intrigued, you can see more of TenshiRisu's art HERE.
Chrisjen Avasarala is my favorite character in the series for a number of reasons. She's incredibly smart, and she knows all the power plays to be made by the different factions in the solar system at all times, and she's able to gauge how dangerous any situation is with extreme accuracy. Additionally, she has some of the best dialogue that I've ever seen. Here's a sample of some of the things she's said.
To Bobbie Draper (a tall Martian marine): "Would you sit down? I feel like I'm at the bottom of a fucking well whenever I talk to you."
“Holden’s an idiot, but he’s not stupid. If he realizes he’s being watched, he’ll start broadcasting pictures of all our Ganymede sources or something. Do not underestimate his capacity to fuck things up.”
“It'd be a better world if there was always at least one right answer instead of a bucket of fucked."
"I feel like I went away for one day and when I came back, everyone was speaking Mandarin."
Chrisjen always has a way of cutting to the gist of any situation, and I look forward to seeing Shohreh Aghdashloo in the role (in the upcoming seasons on Amazon) as she ascends to power during the biggest crisis the Earth has ever seen.