The Mars Trilogy by Kim Stanley Robinson has a lot of ideas for terraforming Mars, and much later Venus. Most of them are just a little past the reach of today’s science, and the main thing holding us back would be money.
The characters used a combination of approaches to warm the atmosphere bit by bit. None of the strategies on its own was enough to reach their goal (breathable air and liquid water on the surface.) One of the first things they tried was genetically engineering arctic plants from earth to survive on the Martian surface.
This series is at least as long as Lord of the Rings, and terraforming was one of the major concerns, so you got to see every gradual step of the process. The author thought of everything, like whether stuff on the surface reflects or absorbs light, and the tiny difference that would make in the surface temperature. Even in an imaginative sci-fi novel, it took 200 years.
You should read it, it’s really cool.