Someone to Watch Over Me

""You go through life talking to God, but what do you do if, one day, God talks back?"" asks a character in this sci-fi psycho-thriller from the author of Lethe. For the characters in this book, maintaining one's identity--and sanity--as technology threatens to replace individual thought with a collective ""meta-consciousness"" is not only a life-and-death matter but a life-after-death matter. The Deep is a sort of mental Internet of brain-wave surfers who ""watch"" their hosts' minds and experiences, slipping in and out at will with the aid of implants or Human Interface Technology (HIT). But Adrien Reyes's supposedly passive Watcher, ""C"" is taking an alarmingly active role that is likely to end with Adrien either supplanted by his Watcher or dead. Sullivan is as skillful at getting inside her characters' heads as they are at invading each other's. She weaves a fine web of narrative voices, deftly shifting among perspectives of her clearly defined characters. Add plain old good writing (""a place more precise than math and more beautiful than music"") to make this novel a brain tickler, despite its rather comic-bookish plot. (Aug.)