Morris's 'Golden Dragon' series is a forgotten gem in the genre of gamebook adventuring. Where the Jackson-Livingstone formula managed to win the day, the effect of that victory for other gamebook writers was disastrous in the long run.
Morris and his collaborators stand out as another major driving force, deserving of a better fate than has befallen them. 'Castle of Lost Souls' is the sixth and final entry in that catalogue, its premise being that as a hired sword, YOU must venture to the castle to slay the demon Slank who has entrapped the soul of your employers' father.
For a 300 reference work (the standard, give or take, length of the average Golden Dragon gamebook), there's a nice balance here between journeying to the destination and journeying within it. Underscoring this is a need to locate five objects that will aid the adventurer in realizing his/her quest. At the level of ease, this is no harder than 'Crypt of the Vampire', but its true beauty lies in its reapproach to medieval English lore.
Recommended for the most jaded Fighting Fantasy gamer. It will provide a pleasant escape.