She marries the (ooh, swoon, he's Russian) boss, MOC, platonic.
She sleeps with her ex, is that adultry? You decide.
That was chapter 1

The GR reviews would lead you to not want to read the book
but
Read the first 3 chapters, yeah, you'll finish it.
Personally, i think that reading the blurb
and /or
Reading the reviews ... not a good idea.
The spoilers will ruin it.
I write that because, here at openlibrary it states:
How would you describe this book? There's no wrong answer here.

Here's the blurb... (you've been warned)

On his terms only...The day Rosa agreed to wear Nicolai Baranski's ring she wasn't so foolish as to expect love. Yet nothing could have prepared her for the aching loneliness of her husband's constant indifference—an indifference that proved too much to bear.
Nico is furious—no one turns their back on a Baranski. Rosa has some nerve if she thinks he will just let her walk away. He'll use every sensual trick at his disposal to bring her back, begging for more

By the end of the book... only you can decide... did she? Did she really cheat?
-D