I cannot recommend this book highly enough. As always, Lawrence has seamlessly woven into her work a wealth of historical details, and in this particular book, biblical allusions. Instead of being intrusive, these details only add to the depth and fullness of the novel. Everything is very accurate, and even the most casual reader is sure to pick up some historical knowledge (though he or she may not realize it at the time!). The Prophet from Ephesus offers the reader an intriguing glimpse into early Christianity as well. Without being preachy or cheesy, Lawrence addresses issues of Jonathan's faith that have needed to be resolved.
A distinctive characteristic that sets her books apart from other historical fiction is her knack for describing settings. Lawrence does not simply rely on visual details--she paints a multisensory masterpiece of scent, sight, and sound that swiftly draws the reader into the novel. When reading her descriptions of places, one receives the impression that Lawrence has been there before (and she has). All of her books have this remarkable quality, but The Prophet from Ephesus is beyond exceptional in this regard.
As far as the plot goes, the series is clearly arcing towards an imminent climax. Romance, excitement and tension climb higher and higher, and at the end of the book, the reader is left hanging off a cliff. Personally, I am torn between longing for the next book to come out, and not wanting the series to ever end!
The Roman Mysteries may be children's books, but in no way does Caroline Lawrence dumb them down for her audience. C. S. Lewis once said, "A children's story that can only be enjoyed by children is not a good children's story in the slightest." By that criterion, The Prophet from Ephesus is a definite success.