It might be. As I mentioned before, Project Gutenberg often offers free e - books and short stories for reading, so there's a chance it could be found there for free. Some independent authors also post their short stories for free on their personal websites or blogs, but I'm not sure if the author of 'Eisenheim the Illusionist' does that.
There are some literary magazines' websites that might feature such short stories. For example, The New Yorker's website often has a selection of short stories, although it's not certain that 'Eisenheim the Illusionist' will be there. Another option could be to search on Goodreads. Goodreads not only has reviews but also might provide links to where you can read the story online.
No, it's not a real story. It's a fictionalized account based on some historical events and figures, but with a lot of creative elements added for entertainment purposes.
The story of 300 isn't completely real. It takes some liberties with the facts and adds elements of fiction to make it more exciting and engaging. But it does draw inspiration from real historical events to some extent.
The story of 300 isn't wholly factual. While it has roots in history, it's been adapted and enhanced to create a more exciting and visually appealing narrative for the audience.