My review of this novel is going to be a bit different from almost all the other reviews thus far. Most people apparently loved this novel, but I didn't. Having read this novel right after the first in the series, I was a little disappointed. I found it to be somewhat formulaic, compared against The Starry Child. The writing itself was fine, but the content just wasn't as strong. For those who don't like any plot elements revealed, there are spoilers ahead.
By formulaic, I mean many elements of this book are almost identical to the first book. For one, there seems to be just one type of relationship that Hanna writes: girl meets boy; girl dislikes boy (sometimes for no apparent/logical reason); boy simultaneously falls immediately in love and can think of nothing but having his way with her and spending the rest of his life with her because she's the most amazing woman ever; girl finally realizes she's madly in love and needs boy and they make a lifelong commitment after having known each other for only a few days. This happened with Rainey and Matt, and in this novel, with Sasha and Kyle. It wasn't believable the first time, and definitely wasn't the second. Even Emma and Malcolm practically fell in love at first sight.
Other ways it's the same as the Starry Child: 1. young characters miraculously begin speaking ancient languages (in this case, Carrie can speak ancient Norse, while Sasha spoke ancient Gaelic; how Carrie can speak Norse, or even why she in particular needs it is never revealed and is one of my pet peeves throughout the book); 2. the family is connected to and partially reenacts yet another legend/myth (although this one is Norse as opposed to Celtic); 3. the youngest family member is overly fond of the new male before anyone else (Carrie loves Kyle, like Sasha loved Matt, although Carrie admits to wanting Kyle to eventually marry her, while Sasha's love was familial); and 4. Rainey is still weak, needy, and annoying (not so formulaic as apparently just a part of her character - what Matt sees in her I will never know. I would have thought she'd gain some strength having learned she's the current reincarnation of an ancient queen.). While reading, I know I picked out more similarities, but I can't remember them all right now.
Anyways, I could carry on with why I didn't like this novel, but there are elements I did like, and I should get to those. The opening scenes, and almost all the scenes with Matt until he is reintroduced to Rainey are all quite interesting and were enjoyable sections to read. I also enjoyed the fairies again, and the legends that are presented. I wouldn't say they were as strong as the ones we met in The Starry Child, though. (And speaking of legends, I couldn't understand why a family so closely tied to an ancient legend wouldn't have tried to research it more (especially since Matt is a researcher at a university) and were instead schooled by Kyle about a story of Rainey's ancestral mother.)
Long story short, I probably won't be reading the next novel in this series (although other reviewers of Circle of Time have complained that they can't find it anywhere, so maybe it's not actually out yet).