THE RESERVOIR and SNOWMAN, SNOWMAN by Janet Frame. 364 pages. Braziller. $7.00.
It is a fairly good rule of thumb to avoid books that come in cardboard slipcases, just as a practiced reader automatically avoids the memoirs of actresses, novels described by their publishers as heartwarming, and books given prepublication endorsements by Clifton Fadiman. The rule is not absolute, but more often than not the contents of a slipcase either have calcified into the classic condition or are so fragile that they need an especially strong container to keep them from crumbling. Most of Janet Frame's stories, sketches and fables in these...