Limitless (PG-13 / unrated)
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This 2011 film is based on the 2001 book "The Dark Fields," which I haven't read. In 2015, there was a TV spin-off from the movie, also called "Limitless," but I didn't see any of that series. And I didn't see the movie until 2019.

There's a struggling writer named Eddie Morra (Bradley Cooper), who somehow has a book contract, but hasn't yet been able to write a single word. And his girlfriend, Lindy (Abbie Cornish), breaks up with him. Soon after that, he runs into Vernon, the brother of his ex-wife, Melissa (Anna Friel). Vernon gives Eddie a pill called NZT-48, which he claims is FDA-approved and will soon be on the market (though very expensive). The pill temporarily allows a person to use 100% of their brain. After the effects wear off, Eddie wants to get more pills from Vernon, but the latter is murdered by someone who tossed his apartment, presumably looking for the pills. Eddie calls the police to report the murder, but while waiting for them to arrive, he searches for and finds the pills himself, which the murderer had failed to find. (There's also some cash and a list of Vernon's clients.)

Eddie soon manages to finish his book (though of course it'll be about a year before it gets published). Now, for me, this would be a dream come true, and I'd start working on the next book, and the next, and the next.... But Eddie decides the abilities the NZT has given him could be put to greater use. It's not exactly clear to me what that use might be, but he'll need a lot of money for it. So he starts using his abilities to play the stock market, and soon gets noticed by a tycoon named Carl Van Loon (Robert De Niro), who gives him a chance to start working for him. But in the meantime, Eddie gets in trouble with a loan shark named Gennady. Despite paying back the loan, Gennady persists in harassing Eddie, after learning about the NZT, which he wants more and more of for himself.

I guess I don't want to say any more about the plot. But it's all reasonably interesting, and Eddie faces several different types of serious danger throughout the film. I definitely enjoyed the movie, but I also don't feel a particular need to ever watch it again. (If I had seen the movie prior to the TV series's debut, I probably would have been interested in watching that, but now I don't feel like doing so.)