I've never seen the 70s version, nor read the book, so this was very much new to me.
As a very basic outline, this series follows several survivors of a deadly virus; as things open we see them dealing with the crisis on an individual basis, but as their lives very quickly converge together they encounter a series of rather unpleasant events and increasingly sinister characters on the way. It's far more than just a sequence of events detailing survival though, as there are strong ongoing themes and the group has certain bonding issues. However, to detail them here would give the game away a bit too much...
It's interesting to read the other reviews as it confirms my thoughts that this was always going to polarise opinion in a big way. It would be hard to be indifferent about this series and I think all of the reviews, whether positive or negative, basically make fair comments. If that sounds like a contradiction, well, perhaps it is a little, but it's all relative to your point of view - personally I enjoyed both series from start to finish, but I can understand why others probably won't. If you can suspend disbelief in a big way (in a very big way in fact) then you'll enjoy this series a lot - it's well polished, the acting and direction is good (for the most part, though there are exceptions) and there is a lot of tension as individual episodes reach their climax. There's also a fair smattering of flame and explosions to keep you action fanatics happy. On the other hand, if you are looking for something that accurately depicts a community learning to live in a devastated world then you will be extremely disappointed as too many practical challenges are conveniently ignored.
I have to admit that I couldn't bring myself to award it five stars because, as other reviewers have mentioned, the politically correct casting was far too contrived (not the fault of the actors, but a consequence of where the characters have been placed); it's not as simple as race and gender either, it attempts this on other levels but I suspect that any half intelligent viewer will find this aspect more than a little patronising. Even someone as open minded as me was struggling to be generous on this point.
Otherwise though, I'm looking forward to the third series.
I've yet to try a repeated viewing, but my thoughts are that it will probably stand up well when you pick it up again in a couple of years or so. My only doubt is that maybe I should have held out for the Blu-Ray version!