In many ways this is a classic in the Cadfael series. I say that in the sense that this book puts forth most of the best elements that are found (more or less) in every book in this series.
There is the sense of place. In this case, the book lets the reader into the world of the lepers. Set aside by humanity, the leper colony of St. Giles proves a multi-dimensional world with an integral role in the plot.
There is romance. As in most of the books in this series, Cadfael lends a sympathetic ear to a smitten pair. In this case, their obstacles are many and it's a fun read as things are unraveled.
And then there is Cadfael seeing what others miss. It is Cadfael that notices a twig of a rare flower near the dead body. Likewise, Cadfael sees some bruising on the body that could only be caused by a certain ring. And more than once, Cadfael simply applies his experiences to discern what human nature is most likely to do.
My gripes with the book are worth a point off. Foremost, the author seems to have forgotten rule number one of detection (surely as applicable then as now) - who would benefit financially from the death? I also missed Hugh's presence. And a most minor quandry -- were they really able to tell time to the point of distinguishing between 6:15 and 6:20 back then???
Bottom-line: a very solid and pleasant read for fans of historical mysteries. Reading of earlier books in the series would be helpful but isn't necessary.