"Desperation" is one of my favourite King books. One of the problems in translating such a novel to the screen is to keep intact the cohesive eerie feel that the whole book has, and the organic way King links the horror and religious aspects of the text. The book deals with David's religious values as a beacon to fight evil, however, in the film David's religion is used merely as a tool to preach. King's book makes religion a supernatural and mysterious force in David's life. In the telefilm Religion is a much more dominant theme particular during the last half.
Mick Garris has done a fantastic job with every thing he has touched, especially King adaptations. This time he misses the mark by a long shot. The acting is quite poor, despite a talented cast. Scenes are never allowed to unfold, but are forced along, thus not giving the viewer a chance to soak up the atmosphere the way a King story demands. The child actor looks like he is perpetually about to cry ( a la Neve Campbell circa 'Party of Five'). Their is absolutely no rhythm to anything in the film, it's all forced.
Bottom line: you can miss this one. However, no one should miss Garris' s 'The Stand' which is an unbelievable work, and a daring accomplishment.