Corrections
The 3 rings for elves, 7 for dwarves and 9 for mortal men were not made by Sauron. They were made by elves whom Sauron had taught.
Sauron's power is not mostly stolen. He has great power over others, but his power is innate to him. He is, in fact, a Maia who is much reduced in power from what he once had. For instance since being caught in the fall of N\ufffdmenor (which he engineered) he can no longer appear in any fair form.
The Lord of the Rings does not go into detail on what wizards are, but Tolkien did make that clear in the Silmarillion. All that is known about them in the LotR is that they look like men, but age very slowly and have strange powers. In fact they are Maia (think something between a nature spirit and a god - Sauron is a Maia) who were stripped of most of their power and memory then sent out by the Valar (think gods). (Gandalf's real name is Olorin.) The purpose of their being stripped of power and memory is that the Valar have learned that showing themselves in power and majesty has the opposite effect from what they want.
Some of the major themes of the book are the nature of good vs evil, that heroism consists of nothing more than normal people doing what they have to when needed, the nature of power and corruption, and reflections on the inevitable passing of history into myth.
One warning about the series. In Tolkien's day it was customary to write in the passive voice. The series is a rich texture of thoughts, feelings, and events. But it deliberately does not attempt to grip with cliffhangers, and force you to read on. It is easy to put it down anywhere, and pick it up later. Readers who are used to a more active writing style may have trouble finishing for this reason.
Cheers,
Ben
