I read this on it's own in the 90s (unaware that it was part of a series, my mom had it lying around) and recalled it recently to re-read. After discovering the rest of the books I'm glad I did!
All of them are good (though some have lack luster endings) but this one is definitely my favorite, and I wish there was more about Chyrie and Valann because I loved their characters and just the atmosphere of the Heartwood in general - though I know now as it's a prequel that it was means to an end.