Readers who criticise this book as disappointing because it isn't of the same calibre as Pratchetts later works are, I think, missing the point. This was Terry Pratchett's first novel, and the reader can trace within it the seeds from which the Discworld grew. I enjoyed it and re-read it from time to time. I would agree that the middle part of the book, when Kin Arad and friends are searching for the answer to their problems, sometimes seems to lack direction - it fragments into a series of vignettes which although entertaining do not always seem to move the plot onwards particularly well. However if such a novel were to be published today by an unknown author, as Pratchett was at that time, I suspect that it would get reasonably good reviews, possibly including some of the comments I have made but almost certainly ending with '...this author has promise and will probably prodice some excellent stuff in the future', and who would say that Terry Pratchett has not done just that?
Criticising this book because it is the product of an unformed talent is the equivalent of rubbishing Equal Rites because the Granny Weatherwax in that book is not at all the same towering character we meet in later books like Witches Abroad, so; read and enjoy, remember it is an early work, and forgive it its imperfections.