The castle is open for visits (entry fee 70 Lei which is about 15€)
Commonly known outside Transylvania as Dracula's Castle, it is marketed as the home of the title character in Bram Stoker's Dracula. There is no evidence that Stoker knew anything about this castle, which has only tangential associations with Vlad the Impaler, voivode of Wallachia, who shares his name with Dracula. Stoker's description of Dracula's crumbling fictional castle also bears no resemblance to Bran Castle.
The castle is now a museum dedicated to displaying art and furniture collected by Queen Marie. Tourists can see the interior on their own or by a guided tour. At the bottom of the hill is a small open-air museum exhibiting traditional Romanian peasant structures (cottages, barns, water-driven machinery, etc.) from the Bran region.
Honestly for 70 Lei it wasn't a bad experience but the whole feel of the castle is almost entirely to play into the cliche vampire/medieval fantasy trope and for tourist to say they have visited a castle.
My recommendation is to visit, but keep expectations at a min. I've been twice now and both times felt lack luster and meh.
If you want a real cool castle like experience and are in Brasov, take the train down to Sinaia and visit Peeles castle. You will not regret it at all. From the grounds, the exterior and the interior, it really is something out of fairy tale or something.
Corvin's castle near Deva is another great castle to apparently vist over Bran but I never got the ability to visit so I can't speak to that as much.