The "Realms of Magic" is a collection of book series, all written by the same Author, a Dunmer by the name of Rulian Sen'rah. Rulian has gained worldwide fame from their success and these books are now widely used in multiple places of Arcane study all across Tamriel.
"Realms of Magic: Arcane" was the first of these books. It was an explanation and exploration of the basics of magical use and magical theory. It has become a core text in the use of teaching the newest of magical practitioners.
"Realms of Magic: The Schools of Magic" was the first series written, after the success and approval that Realms of Magic: Arcane received. It was a 10 book series that began with Realms of Magic: Abjuration and included other sub-titles, such as Conjuration, Divination, Enchantment, Evocation, Illusion, Necromancy, Transmutation, Restoration, and Mysticism. There was mixed approval, but overall appreciation for these books. They approached the different schools of magic, but not just from the Imperial view of the schools of magic. The final two books of this series spurred on the inspiration for the next.
"Realms of Magic: Magical Themes" was the second series written and was inspired by the books Realms of Magic: Restoration and Mysticism, where the topic was already touched on, of mixing focus on multiple schools of magic, to create a blend of practice to fuel various different kinds of magical practitioner that could be found all across the world. Here and there, these books define the difference between Imperial branded magical identity and what the author describes as the true differences between magical practices. It was a 4 book series that actually began with the last two books of the previous series, thus making it actually a 6 book series. Such titles include: Realms of Magic: Entropy, Spiritualism, Blood, and Alchemy.