THE CLOUD OF UNKNOWING
The apparent normalcy of the characters at the beginning of the novel changes, page by page, as the author gradually reveals their mental instabilities and their propensities and motives for murder. Soon eerie, bizarre behavior becomes the norm, and it's difficult to distinguish reality from delusions.
Diana becomes strangely unbalanced when she and Mark separate, and she vandalizes his car. Dave, an attorney, wants to help her find justice even though he's becoming increasingly convinced that she might have murdered their father years ago -- and might now harm Mark or herself. (Harcourt, Jan., 320 pp., $24.00)