This third installment in Dr. Russell's series (The Devil, Satan, Lucifer, Mephistopheles) comes to the Middle Ages, which means that we are well beyond source material in Canaanite and Jewish legend and now into the development of the devil in Patristic literature, and onwards.
On the plus side this is the historical period where Russell is an expert so you would expect it to be the strongest of the three volumes. On the minus side, in this volume, as with the others, one is constantly uneasy that the historical perspective is being underpinned by the author's own belief in a literal fallen heavenly being, and too often it is not clear whether the focus is medieval society or metaphysics.
Incidentally, anyone buying this book because of the word 'Lucifer' in the title will be disappointed that Russell does not address how the specific concept of 'Lucifer' developed from Origen and Augustine onwards. Neither here, nor in the previous volume 'Satan', does Dr Russell deal in any depth with the process by which a name which for the first 4 centuries of Christianity was used as a title of Christ (because the Latin word Lucifer appears in the Latin Vulgate as Peter's "day star"), to the point that early Christians used to name their children Lucifer (eg Bishop Lucifer of Cagliari), suddenly by the 5th and 6th centuries was being used as a title for a fallen angel (based on Isaiah 14:12 being reapplied).