I think the atmosphere would have been pretty breathable

HELLA breathable bruh..

The couple of people who've been on the moon have seen that kind of emptiness

but plants wouldn't conquer the land in a serious way for at least another 60 million years or so
...
Eons would pass before the first plant set root at their feet.

Pretty sure the mountains will still be there. Spoiler alert. I started at the end of the book.

you would be the only being to ever observe them in their formative years.
...
The sterile and desolate emptiness would be beyond human experience.

That's badass though. Except that we might be returning to that sterile and desolate emptiness here shortly.

Also, don't forget that fungi, algae, and lichen colonized dry land before the plants arrived, paving the way for them by eating rocks and pooping dirt.