What draws visitors to Monhegan-a small island off mid-coast Maine? It is not just the island's timeless atmosphere and beauty but the quality of the light that has always been a magnet to artists and photographers, as well as to vacationers. Now nature photographer and writer Mark Warner has produced a keepsake-cum-guidebook that is a must-have for anyone who visits-or dreams of visiting-one of Maine's most fabled islands.