When it comes to lore, few other franchises at any time in media history can compete with The Lord of the Rings. The original movies had to leave a lot out in order to fit into the epic trilogy that exists today, and the filler that made The Hobbit into three movies came from these various other sources.
Tolkien wrote extensively about the ancient history of Arda and the beings that created it, a time known as the First Age. This is also the time that the Maiar came into being, and five of these would eventually become Wizards in Middle-earth. Saruman was among the most powerful, and that's one of the few details about him that was unchanged between his character in the books and the on-screen adaptations.
6 A Maiar Of The Valar
The Maiar were spirits that served the Valar, and in the very beginning of creation, they were numerous. They came to Arda with the Valar, so they weren't created there but came through the astral firmament with their masters. The five Wizards are the most well-known examples, but Melian, the wife of King Thingol, and Sauron, Morgoth's right-hand, were also Maiar.
The Wizard called Saruman was sent to Middle-earth to fight the darkness of Sauron. Before then, he served the Smith of the Valar, Aulë, in the Blessed Realm of Aman. This is why Saruman the Wizard was so adept with smithing, craftsmanship, and machines. The Maia called Mairon was also a servant of Aulë, and he was eventually recruited by the Valar Melkor to become Sauron.
5 His Plan For The One Ring
The adaptations touch on this important detail, but there hasn't been time for it yet, and there hasn't been a movie or series in which this is important to the plot. This might change in the new Amazon series, which deals with events of the Second Age when The Rings of Power were forged. This predates Saruman's arrival in Middle-earth, but the forging of the rings is connected to his Valar master, Aulë, giving him intimate knowledge of how to craft them and the power they hold.
One of Saruman's many titles is actually "Ring-maker" and he took it partly to complete with Sauron. He actually tried to forge his own One Ring using the lost art of Eregion to both emulate and compete with the Dark Lord.
The Wizard's ultimate plan in the book was to take the One Ring for himself if possible, even if it took a long time and he had to serve as Saron's vassal in the meantime. In the movies, he's portrayed as more of a traitor and servant of Sauron, but they were still both Maiar of equal standing.
4 His Alternative Names
Gandalf the Grey had a few different names in Middle-earth, such as Mithrandir among the Elves, and less flattering names among the humans, including The Grey Pilgrim and Gandalf Stormcrow. Saruman also had a few nicknames in Middle-earth, and in the Kingdom of Valinor, he was known by a different name.
In the days of the First Age, Saruman was originally named Curumo, and he was also known as Tarindor. He volunteered to travel to Middle-earth and defend it from the Dark Lord, and this initiative is why he was named the Chief of the White Council. His elven name was Curunír, and it was the humans that named him Saruman.
3 The Battle Of Isengard
It's not that this is left out of the movies, being one of the pivotal events in the plot, but many of the details were tweaked, twisted, or changed completely to fit into a typical three-act cinematic structure. It's nice that the poetic justice of a Wizard obsessed with machines being defeated by a marauding horde of angry trees isn't lost.
In reality, the Ents were anxious to attack Saruman for what they saw as a long and hideous betrayal that had gone on for centuries. In spite of his defeat, his voice still had some magical power, and he was able to convince his old friends the Ents that they should let him go, for he was an old man now with little power.
Not only was he allowed to leave, but Grima Wormtongue departed with him, and it soon became apparent that he was far from harmless.
2 Sharkey And The Scouring Of The Shire
Saruman betrayed Sauron's trust by maintaining that he knew nothing of Bilbo Baggins or the Shire when in truth he had taken careful note of Gandalf's wanderings. After the Ents let him go, he went the way the Fellowship had come. At one point, Gandalf and Celeborn encounter the two of them, bickering as they wander along the road like beggars. Eventually, Saruman reached the Shire.
When Sam looked into Galadriel's mirror pool in the movie, what he saw was a vision of the future of the Shire should the quest to destroy the One Ring fail. In the book, however, what Sam saw was a vision of the near-present. Saruman had taken over the Shire using the power of his voice and a smattering of his broken military forces and a gang of ruffians.
By the time the Hobbits of the Fellowship had returned to the Shire, it was almost completely changed into an industrial wasteland. It takes all of their forces to expel Saruman, now known as Sharkey, and build back everything he destroyed. This final battle takes up a few chapters at the end of The Return of the King.
1 His Death
The moment of Saruman's death isn't so different than in the movies, as he is betrayed and stabbed by Grima in both versions. However, in the movie, he falls from Orthanc tower and his story ends. In the book, he dies much later, and as one of the Maiar and can't really suffer from a conventional death.
When he is stabbed in the book, his corporeal body, or what was left of it, simply fades away when he is killed. It is said that his spirit, now powerless and without form, tried to turn back to the West and return to its original master, but a stiff wind blew it back. Like Sauron, Saruman is bound to wander aimlessly in Middle-earth as a weakened spirit until the Valar deem otherwise.