Be aware that this is a single disc release not 2 as stated in the description but there are still plenty extras included here, enough for most tastes.
The story has quite a few strands working together the Cybermen trying to use Halley's comet to destroy the Earth, prisoners on Telos trying to steal a ship to escape, a fake bank robbery and Telos' original inhabitants the Cryons seeking revenge on the Cybermen. Not all of these work to the same standard and the first episode is generally viewed as being the better of the two.
Like many people I did not take to the Cryons at all, that might have changed if they were filmed as they were originally conceived but to me they just look silly but the chunky Cyber-controller makes up for some of that disappointment.
With decent actors like Maurice Colbourne and a nice vein of humour largely focused through Brian Glover, both of whom are now sadly deceased, oh and Peri's pink outfit which is fairly well discussed in the very interesting commentary by Colin Baker, Nicola Bryant, Terry Molloy and Sarah Berger who reveal many things including that there was an underwear thief at the BBC at that time.
The extras include a documentary about the making of the show which highlights the disagreements over several plot areas. It was meant to be slightly more violent, the Cryons were written as males, there's even dispute over who was responsible for coming up with the actual plot itself.
There's a nice look at the history of the Cybermen that examines how the design has changed over the years as budgets increased and a brief look at the possible future of cybernetic implants in humans.
As a whole it's a pretty decent package and one that I will be watching fairly often.