No, you donĀ“t necessarely have to. But it would have helped me to place Alan Grant somewhere in time. I took me some time to figure out that he might be lying in the hospital during the 1950s (the time the book has been written).
Tannat, if you do feel the need to read the previous ones in the series before this one, you can skip The Franchise Affair (#3 in the series). It is part of the series, but Inspector Grant is hardly in it. I am looking to read books #1, #2, #4 and #6 at some point, too.
This one did my head in; I kept waiting for a crises or a climax to the plot and there isn't one. I enjoyed it - but I'd have enjoyed it more if I'd known enough about it to not expect the typical. It's definitely one I'll get more out of the next time I read it.