Depends on what you are really interested in? A good entry point into magic could be "Modern Magick" by Donald Michael Kraig. It gives you an introduction into western magic, its main rituals, and also its main cosmological backdrop (i.e. Hermetic Kabbalah). This will set you on a good path for many other traditions in western magick, such as the grimoires, Golden Dawn, Witchcraft, etc. I used it as my own starting point and the way the author talks to you makes it very accessible.
You could also try some beginner books on witchcraft if you like, these can be quite beginner friendly as well. But my vote still goes to Modern Magick because it can set you up for witchcraft and many other traditions. When you are more advanced, feel free to look into "Initiation into Hermetics" for a nice syncretic blend between eastern and western practices along with powerful practices for the elements.
If you want a dose of something purely practical without any theoretical backdrop, you can find something in the modern grimoire genre. Typically these books are extremely light on theory and contain simple quick practical magick rituals that you can use immediately for real world results. The rituals can usually be done in minutes, though there are a lot of people that would argue against this. Still, exploring books from The Gallery of Magick is always a good start for this, especially their "Words of Power" books which are very simple to use. In my experience, their magick does work (somewhat) and they are probably the best way not to get hung up on theory. Many people just need a simple taste of world world results and then they will be satisfied with their dive into magick. This is a good way to do that.
Again, there are many different approaches to starting, but these would be my main suggestions for "theory" and practice. Make sure to actually put what you read into practice in order to truly gain benefits out of it.
