Every once in a while a book comes along that defies categorization. Such is the wonderful slithering conundrum that West Rutland author Jon Furman poses for booksellers with his “Timber Rattlesnakes in Vermont & New York.”Its title and 208 extensively footnoted pages argue for placement on the shelf with other nature guides. But there are easily a half dozen reasons Furman’s book deserves a much wider readership, not the least its stunning cover photo of a yellow morph timber rattler, its fierce glare through yellow-slitted eyes striking us – as it were – with fear, fascination and repulsion.