Beast is a so-so movie, and the decision when writing about it is whether to focus on what works or what doesn't. If I talk first about what's good, it will sound as if I liked it more than I actually did. If I talk first about what's not so good, it will sound like I didn't like it at all.
So ... to the good. Idris Elba is always a good thing, and here is in a mode we don't usually see: he's scared. He plays a widowed doctor who takes his two daughters to South Africa, where their late mother grew up. Elba and the two actresses playing his daughters (Iyana Halley and Leah Sava Jeffries) make a believable family, trying to put their lives back in order. The titular beast is also great, and the CGI is seamless ... you forget it's not a real lion. It's also nice that the Beast isn't an alien from outer space or a mutant created in a laboratory. It's just a lion, big, pissed off, but a lion nonetheless, and someone even scarier as a result.
And yet I didn't care for the movie. Part of the problem lies in those daughters. It's completely unfair of me to complain that their vocal fright at their predicament is annoying ... I'd be just as scared or more so ... but honestly, as some point I just wished the lion would eat those damn kids. Also, to establish the cranky independence of the elder daughter, she is constantly doing dumb stuff that puts her in danger. This adds to the thrills, but it also makes her character seem pretty stupid (when she clearly is not).
Beast is by the numbers, and is perfectly satisfactory as a Saturday afternoon time waster at home on the couch. I won't say more.