This is a fantastic series which starts with Waterfall, then continues with Cascade and Torrent. Bourne is a Novella that continues the story where Torrent left off. It's about time traveling sisters who go through things they never dreamed possible. It's in the young adult category but i think it's a book for anyone from teenagers up. I'm 49 and I couldn't put any of these books down. They were excellently written, lots of action,romance and humor. You'll fall in love with many of the characters. After reading these books I can honestly say its one of the best stories I've read in a very long time and I don't want it to end. I want more. If I could give more than 5 stars I would.