I read a couple of Arthur C. Clarke's books when I was younger but Childhood's End wasn't one of them: I can't compare this to the source material. This is a 2015 three part mini-series from Syfy, with each part running roughly 1h22m.
The series starts in the current world (mostly modern America) with the arrival of the Overlord's ships which hover over several major cities throughout the world. Kerellen (Charles Dance) - who claims to be the "Overlord for Earth" - speaks to pretty much everyone on Earth, explaining that they will usher in a new age of peace, a utopia. He recruits a farmer named Ricky Stormgren (Mike Vogel) to act as a representative. Over the next several years, the overlord's promises are seen to be coming true - although Kerellen refuses to let any human see him, saying that they aren't ready. Ricky stays with us through the second episode, but astrophysicist Milo Rodericks (Osy Ikhile) is our main protagonist through the second and especially the third and final episode.
The story moves through phases, each with several characters. Most major characters are seen in all the episodes, but some episodes concentrate more on certain characters. It's an interesting and fairly good if rather bleak look at what might happen if we encountered an alien race immensely more advanced than we are.