This is the third book in the Tudor Wives trilogy by Laurien Gardner, titled Plain Jane. The story begins with her somewhat unhappy childhood, then following is her service to Queen Catherine of Aragon, through Anne Boleyn's seduction of Henry, and finally to Jane's rise to royalty, followed by her imminent death after bearing Henry's only son.
I personally really enjoy Gardner's writing. She definitely takes some liberties as far as historical accuracy goes, but that's why this is classified in the genre of Historical Fiction. It's not supposed to be 100% authentic. I've never read anything about Jane Seymour save for the mention of her taking Anne's place in novels that revolve around the Boleyn family. It was refreshing to dig deeper into Henry's past and his romances with a wife other than Catherine and Anne. As it turns out, Jane Seymour seems to be climbing her way up my favorite interesting historical figures list.
I would recommend Gardner's series (though I have not been able to get my hands on Catherine's novel: The Spanish Bride). Her books are very easy to read and keep you hooked and wanting to see what happens next. It is the perfect blend of history, fiction, and romance. In short, it's right up my alley. And if you enjoy Philippa Gregory or Diane Haeger, you'll probably enjoy Laurien Gardner also.
Next I'm taking a little bit of a break from the historical world... I know, I know. It sounds crazy. But I decided that I need to get a Jodi Picoult and another Nicholas Sparks under my belt. Hmm, then maybe I'll tackle another one of Diana Gabaldon's masterpieces. The possibilities are endless.