First be warned that you have to like historical mysteries, particularly those that take place in medieval times - life was slower back then, and news travelled even slower (depending on the weather, the method of transport, the level of political strife, the condition of roads etc). All of these conditions are brilliantly evoked in THE VIRGIN IN THE ICE, which contains several surprising subplots, including revelations about Cadfael's past.
Now to the review proper. If this is the first Cadfael you are reading, you might find understanding some expressions and the society he lives and works in somewhat hard to follow. Basically, the story is set in the middle of a bitter English civil war between two grandchildren of William the Conqueror. Cadfael is a Welsh soldier turned monk. His chosen specialization in herbs and gardening is combined with his knowledge about warfare (and wounds inflicted by men on each other) and the real world to make him a formidable medieval detective. Furthermore, as a monk, he is relatively protected (as far as one could be protected) from physical harm on either side. Cadfael's duties keep him mostly in one town - Shrewsbury and its immediate environs, but he has been known to travel. While most of the Cadfael mysteries are set close to Shrewsbury (a real town near the Welsh border), in this particular book Cadfael will travel closer to Ludlow, a major castle to the south of Shrewsbury. During his sojourn, he will have to solve several mysteries, such as the identity of the young woman he finds dead and encased in ice (hence the title), the name of her murderer and his motive, the whereabouts of two noble orphans whose uncle belongs to the opposing side in the war, and the whereabouts of a band of robbers terrorizing the countryside. Oh, and find out what exactly happened to a badly injured young monk.
If you have read Cadfael before, you will still find this book enthralling because of the deft way it weaves politics, religion, petty (and not-so-petty) crimes against a sharply delineated local backdrop.
Some readers find Ellis Peters's endless descriptions of the countryside boring. I find them enthralling and only wish her publishers would get the maps right in the paperback versions (I have discovered the map for one book in another). One of the charms of the Cadfael series is the discovery of the Shropshire geography in medieval times, made all the stronger by the fact that the now deceased author was a local. Geography in virtually every Cadfael story is crucial to the plot, and not just backdrop as it is in so much historical fiction. And yes, geography - notably the topography and the weather - was very important to medieval people. It mattered which path you chose in the face of an approaching storm - one choice led you safely (if rather cold) to a place of refuge such as an abbey or a cottager's farm, while another could lead you straight to bandits.
Virtually every Cadfael book has young lovers in it, and this is no exception. Here the young lovers are crucial however to the mystery, and their romance comes about as part of the plot, not incidental to it nor preceding it. If you don't like any romance in your mystery, I don't think this particular title offends very much - the relationship is hinted at, and is not a major part of the story.
This particular title, along with ONE CORPSE TOO MANY, is strongly recommended to lovers of historical mysteries.