Via Radiotimes.com:

Ever since Star Wars Episode VII: The Force Awakens hit cinema screens last December we’ve been asking questions. Lots and lots and lots of questions.
And now it seems as though we’re about to get a definitive answer to at least one of our queries when a new novel is released next month.
Bloodlines – a new Leia-focused novel written by Claudia Grey and due for release on May 3rd – is going to give quite a bit of insight into the franchise’s new big baddies, The First Order.
Plus, it’s going to reveal how and when the Resistance was formed – according to StarWars.com at least.
“One thing we know about Leia is that she’s always willing to do the work. She just wants to Get Stuff Done. So how does the Resistance figure into that?” an official teaser on the website reads.
“What events would push Leia to break away from the Republic she has dedicated herself to serving? And who was there with her from the beginning? There’s one way to find out…”
And that’s not all. Bloodlines is apparently going to feature a MASSIVE revelation about one of the galaxy’s best kept secrets. And there’ll be more Han/Leia relationship drama to devour.
We’re ready and waiting to be taken far, far away.