Single ingredient cookbooks--featuring apples, yogurt, or chicken--should reveal in a fresh way the hidden potential of the subject. Taking up the lemon, Casson and Lee present a humdrum collection of recipes with-lemon-added--often only as a garnish. Meanwhile, we are not told how to remove the zest (the yellow covering) or the pith from the peel, how to glaze the peel, or how to candy the slices. There is no recipe for lemon tart, marmalade, or jelly, and no mention of the fact that lowsalt dieters can replace the salt in their spaghetti water with lemon juice. The recipes are sometimes unreliable (duck not pierced for crispness, scallops overcooked)--and we don't believe that a lemon-based salad dressing flatters wine more than a vinegarbased one. There are a few appetizing, original recipes (fresh fruit soup, lemonbacon broccoli), but not enough to sweeten the whole offering.