This YA historical fiction time travel book continues the story of Meagan, a horse-loving teen who finds herself transported through time by her horse, Promise. Her previous adventures included riding with Mongols, Cortez, and French royalty, among others. In this final book of the trilogy, she finds herself on western cattle drive in 1861, at a New York horse race during Prohibition, a Polish cavalry charge during World War II, the 1968 Mexico City Olympics, and then the year 2078 -- a future where horses are nearly extinct.This book was definitely my favorite of the series. The storylines seemed to flow together more easily, and Meagan seemed to mature and learn from and make connections from her experiences. She became more in control of her own destiny, rather than the previous novels, where it seemed as if she were just going along with everything else, biding her time until she got back home. The author also included a romantic interest, which helped develop Meagan's character -- showing a new side of her, expanding her emotional range, and tying her to the past.Although the main character is Meagan, the story definitely revolves around the horses. Even with my incredibly minimal knowledge of horses, the book was fairly easy to read, particularly with the handy glossary in the back. Even though I wouldn't consider myself a horse-lover, the author really makes the reader connect with the horses, making each of them essential characters in Meagan's life.The critiques I have of this book are very few. I do wish that more time were able to be spent in the time periods following the Civil War. The first half of the book all takes place in the same era, and while I loved that part of the story, I couldn't help but feel that the following jumps through time were a bit too rushed -- I wanted to know more! Also, although I loved how the story ended, the time travel fan in me had some reservations about the epilogue...When Meagan arrived back in her own time period, she had not aged! She came back the very day after she left, which made it easy for her to pick up where she left off in her life, but bothered me to no end. Then, when she goes back in the past again, it's unclear what age she arrives there. Though the author mentions an age difference between Meagan and her husband, he must be about eighty years old? And is she still 15? I must have read through that part a half a dozen times trying to make sense of it -- If she were 15 when she went back to 1920, then in 2012 she would be 107 years old?) It didn't seem in the first book that Mrs. Bridgestone were THAT old! It also didn't make clear when her husband died -- before or after Promise?Overall, I really ate up this adventure story, and didn't want to put it down. I thought that this really was a great series, even despite the fact that I don't tend to like reading about horses. I'd highly recommend it to horse fans, history buffs, and those looking to learn something new! Also, my thanks to the publisher for the advanced review copy!