PHANTOMS OF THE ISLES by Simon Marsden (Viking: $24.95; 128 pp.). Don't believe in ghosts? Don't want to? Then steer clear of "Phantoms of the Isles," Simon Marsden's second photo-essay book (after "The Haunted Realm"). The man is a wizard. In roaming the misty moors and shrouded coasts of Scotland, Ireland, England in search of restless spirits, Marsden seems to have developed an unearthly knack for filming ectoplasm itself. His forte is castles--Glamis, Tintern Abbey, Allerton Park (above)--but his subtext is the wraiths of the violently departed: a phantom harpist hanged by his own strings; a misshapen heir entombed in a stone wall; a defenestrated servant who still taps on windows. . . . Stare at any one of Marsden's magnificent, malevolent photos long enough and you'll swear something moved.