This is a fairly typical end-of-the-world scenario where a plague kills a significant portion of the world's population. It's unusual in that only half of all people are susceptible depending on whether they catch the deadly strain on the equally likely harmless strain first. Of course, the following chaos accounts for a good proportion of the people that survive the initial plague.
The story centres around a married couple who are on the verge of splitting up when the first victims are reported. The man is a journalist and the woman is conveniently an expert virologist working to stop the plague. The story features the aftermath of the plague in the UK, but could be equally applicable to most countries.
Quite a decent story, but nothing unusual.
Note that this book was published as 'Survival Margin' in the US, which I only realised when I bought both books and it all seemed very familiar when I started reading the second one!