Lady Astrid was originally introduced in the Portia's story "To Wicked to Tame". She is introduced again in "One Night with You" as Jane's friend. Though all of these books are separate and not grouped as a series, I would try to read them in order if it is possible. I would definitely try to read "To Wicked to Tame" at least before reading "Surrender to Me" since Astrid's actions in that book have a lot to do with why her character does/acts the way she does in this book. Bertram & his sister Portia Derring are characters introduced in the book "Once Upon a Wedding Night". Again all these books are written to stand alone, however if you are able to read them in order it will be much more enjoyable for you.
I didn't think I would like this one but I did. The only thing is that towards the end it gets a little frustrating with Astrid's insecurities making her throw other women at Griffin. But that resolves itself rather quickly and I love how Griffin doesn't back down from her.
Amazing thing is I usually hate it when sex is used to win an argument but somehow Jordan does a really good job of that here.
Don't expect Astrid and Griffin to have long bonding talks because they don't. They kind of fall in love with each other because of how they act to circumstances. Well, and the steamy sex probably helped a lot.