He initially wrote science books for the non-specialist, but had difficulty interesting publishers in these works. In contrast, his writings on UFOs and the supernatural were quite popular. In the course of researching his work, Cohen developed a genuine interest in the occult. However, despite having crept around haunted houses, attending séances, and spending a night in a graveyard, he admitted he had never seen a ghost. Though Cohen was intensely interested in the UFO phenomenon, writing several books on the subject, he was an admitted skeptic; he maintains though that the lack of conclusive evidence does not disprove anything.