"42" was easily the best looking Doctor Who episode ever, with beatifully designed glowy sets, lots of fire and blinking lights and eldritch glowing eyes, more great-looking, sweating, intense actors, all wonderfully shot by Doctor Who veteran Graeme Harper.
Plotwise, though, it was a bit routine. Just another "base under siege with a time bomb" story, and the fact that the time bomb was a sun doesn't work to disguise that at all. Then again, this was a Chris Chibnall script, so expectations were low, and in fact expectations were exceeded. The story did not embarrass like Chibnall's ham-handed writing on Torchwood. Thankfully, little attempt at characterisation was made and the emphasis was all on keeping up the suspense and on the business of running around, issuing commands, opening doors and trying not to get burned into vapour. On that basis it worked well, even though very little happened that was at all remarkable.
On the whole, better than it could have been, and mostly made memorable by its looks.