So, this isn't exactly a review, so much as its my pondering over a book, and this was perhaps the closest forum for it.
Sagas the Demonspawn is an old, old (1984 or so) series of gamebooks by Irish author J H Brennan (also a noted author of occult books). I've been playing over book 1 in the series; I did play #2 (a bit) and #4 many years ago from the local library, but don't actually own them, so this review focusses on book 1.
The Demonspawn game books are similar to say Fighting Fantasy gamebooks, though they're written under the assumption that you're playing a particular character, a guy called Fire*Wolf. (the "*" apparently represents some sort of unpronouncable guttural noise), a barbarian. As you can tell from the name of the series, you're going to end up fighting the Demonspawn, monstrous creatures created by sorcery and vitalized by possessing demons.
The game system there is a bit more intricate than the usual gamebook game system, enough that I found it interesting anyway: you have 7 basic attributes - Strength, Speed, Stamina, Courage, Luck, Charm (same-sex Charisma), and Attraction (opposite-sex Charisma) which are each rated as a percentage between 16 and 96 (2d6x8), plus a special attribute "Skill" which starts at 0 and increases by 1 every fight a character wins. A character's hit points ("Life Points") are equal to the total of all their stats, so an average starting Fire*Wolf has 392 Life Points (!), +1 for every skill point they get - and yes, how sexy you are adds significantly to your life points. Stat checks are made by rolling under your stat on 2d6, multiplied by 8. Its a bit, uh, complicated. Its also weird in that the text always describes Fire*Wolf as a hulking brute of a man, and there are quite a few sex scenes built into the text here and there, but all his stats are completely random -so you might actually roll him up as a feeble weakling with a face that scares small children.
Combat works by rolling 2d6, adding +1 for every 10 skill points you have, and another special +1 if your Luck is 72 or more. A roll of 7+ normally hits an opponent, and each point over gives 10 points of damage. What I found interesting when I played was that because of this, SKILL greatly adds to the average damage. Combats are still pretty hard though (particularly if fighting more than one opponent)
The adventure itself has fairly well-written prose descriptions of crap and the world ("Harn", no relation to the Harn in Harnmaster tho) isn't bad - I think in general it managed a fantastical feel, but with the magic clearly an ornamentation rather than a basic construction material (if that makes sense). The adventure is very linear...wandering off the tracks gets you killed painfully...but I find that forgivable in a solitaire adventure. There are a number of puzzles and things in there at least in the first book (you'll notice there's no "INT" stat - you the player have to do all the thinking).
Fire*Wolf's background is a bit wacky.
[spoiler alert]
Overall rated a "6" although some of this is perhaps misguided nostalgia for my misspent youth. I forgive most of the game systems' quirks due to it being written mid-80s and found it enjoyable despite them, but I can't expect most gamers to be so forgiving (picking on mechanical flaws in anything from the era being like shooting fish in a barrel ...or maybe going fishing with hand grenades). On the plus side if you do find this around the place, I imagine it would be in a bargain bin for 1/2 of a pittance).