>>20288
>isn't this fringe territory?
I would say that the lines between the two are often blurry, more usually separated when, in essence, they are intimately entwined. The paranormal and the esoteric are fields both which are analyzed through the deconstructive facilitation of variety upon belief, fact and fiction, and which concern themselves with different dimensional focuses upon simply alternating layers belonging to the omniverse.
>where to begin?
If you don't have a particular focus in mind, I would scope out the General mega book listing. There are lot of subjects there, from general outlooks upon Mesopotamian deities to the Qabalah, from numerology to sorcery in ancient Scandinavia. Other subjects are also available, sometimes broad and other times specific, such as alchemy and psionics. The Left Hand Path section is a very general section covering different extremely individualized approaches towards sorcery and magick. Where the two sections differ are their qualifiers upon aesthetic/ magick and its utilities.
Grimoires are usually esoteric spell-books that sometimes may or not build off of exoteric practices, either historically or contemporarily. Sometimes they are explicitly about a current/ hierarchy/ set of spirits, and other times they approach a broad amount of subjects with an esoteric and sometimes scholarly perspective. The Satanism section deals with the many forms and introduces both philosophy for the curious and for the practitioner, to both discard falsities and increase wisdom. Due to a lack of exposure and popular misunderstanding, only very certain forms of Satanists are widely known, much less understood. They branch out in vastly varying forms and there are a lot of outlooks, from Gnostic to Transcendental to Atheist to Traditional.
Demonology covers subjects which are very similar to what paranormal researchers look into, i.e. the energies of the potentially abnormal omniversal occurrences. They also deal with both transformative psychosocial primal energies and esoteric/exoteric existences of paranormal dimensional beings. Luciferianism often centralizes upon enlightenment, individualism, exploration of inward and external transverse beckoning, and being a bright flame. Cthulhu is about mystery, the unknown, about the raw and primal forces within the subconscious and its dimensional relations to both potential and other thought-forms, such as egregores and god-forms.
Books upon the dead concern subjects which are also extremely aligned with paranormal research, being that one formation can be considered the spiritual exploration of the paranormal, and the other popularly conceived form can be understood as witnessing or observing the 'dead'/'unknown entities'/ 'spirits and ancient ones'. Draconic magickal studies are multifaceted and vastly differ in their explorations. Some practices refer to simply the hereditary impulses and ancient powers within our species, while others refer to our connections to entirely distinct and yet uniquely acosmic and cosmic deities/ entites/ presences.