Since I have little familiarity with the original Slaine comics from the 1980's I cannot comment as to whether or not the present novelization follows the graphic source materials. From what I can gather the original comics were at least partially based on artists' interpretations of classic Irish literature as the "Cattle Raid of Cooley" (Tain Bo Cuailnge) and sections of the "Book of Invasions" (Lebor Gabala Erenn), and to a lesser extent gleanings from Greco-Roman literary references to the historical Celts. It would be much more advantageous to spend one's time studying the above two texts in any number of translations from the Old Irish. As a stand-alone book, "Slaine: the Exile" leaves much to be desired.
The author has a professional obligation to provide us deep and compelling prose not only concerning the protagonist and his kin, but their environment. On both counts Savile has failed us.
Surprisingly, there are no extended, detailed descriptions of the world in which the characters live, here styled the "Land of the Young" (Tir nan Og). Not even a graphic of a map is presented in the book. This is remarkably odd, since the majority of fantasy-oriented fictions are furnished with this convenience. Nature-worship, through a Mother Earth Goddess (Danu) in her various avatars, is the core of their belief-system, and yet the characters' surroundings, the natural world in which they live, is hardly painted at all, and where it *is* mentioned, only with the quickest of anemic brush-strokes, offering the reader a hasty silhouette sans any crucial details. The author, due to his ineptitude with the English Language, fails to impress upon us the characters' awe of nature, and even fails to provide us the utilitarian necessity of a simple map of their world--be it in prose or by visuals. One way to remedy this deficiency would be to have a small chapter in the form of a dialogue between the learned druid Cathbad and his young apprentice, Dian, educating him and us on the lands occupied by their tribe, the layout of their capital Murias, other major habitations, natural features of note (mountain ranges, rivers, fords, lakes and seas), as well as the relative situation of their various allies and enemies. In this way not only Dian learns in the story, but so do we. Tragically, this idea did not occur to Savile.
After a series of contests before the watchful eyes of King Grudnew, the main character Slaine is later initiated into the ranks of the elite warrior band called the Red Branch, but we are given no inventory of the skills, no glimpse into the rigorous training undoubtedly hammered into them. In the "Tain" weapons, shields and armour are respected, honoured, and provided with individual names as if living things, but here are not treated as anything more than inanimate, mundane tools. Of the marvelous feats that the Irish hero Cuchulainn could execute, only one is mentioned, and that being the Salmon Leap. Slaine's warp-spasm (riastrad), a berserker's paroxysm whereby the protagonist can swell up into a terrifying mass of muscle, is described nowhere nearly as effectively as in Kinsella's translation of the "Tain."
In terms of the language, it is rushed, sloppy, without any indication that the author had any interest or passion for storytelling. The author speeds at breakneck pace through each scene, as if he were desperately trying to complete a college term-paper that was due in the morning rather than drawing us deeply into a strange and vibrant world that is a fusion of the late Ice Age and the European Celtic Iron Age. Perhaps Savile did not know any better. Perhaps he did not care. Furthermore the text is peppered annoyingly with modern colloquialisms, jarring and inconsistent with a supposedly "ancient" milieu. Slaine's amorous exploits also are written as if they were nothing more than the casual, shallow conquests of a Guinness-soaked pubcrawler. Again, for a character who supposedly worships a supreme Goddess, his interactions with females ring shockingly hollow and disrespectful.
In conclusion, I cannot recommend this book to the curious, unless they have a masochistic need for yet another exemplum of threadbare wordsmithing and heartless storytelling. If you want insight into the ancient Celtic world please consult the "Cattle Raid of Cooley", or the "Book of Invasions". Mongoose Publishing offers a well-designed game book ("Slaine: The Roleplaying Game of Celtic Heroes") that is full of much more flavour and information on the Land of the Young, including a functional map. Another RPG book with real-world information is "Celtic Age: Roleplaying the Myths, Heroes and Monsters of the Celts", by Avalance Press.