Where to begin a series?

When reading a series of crime novels, is it necessary to begin at the beginning? In the past, it hardly mattered. Poirot and Sherlock Holmes don't exactly 'grow' as characters. Nor, really, do Father Brown or Gideon Fell or Jane Marple. But Lord Peter Wimsey did develop, in the books featuring Harriet Vane, and Dorothy L. Sayers set the trend for treating detectives as people who would change over time, almost (if not quite) in the way that people do in real life.

Now, it is common for detectives' lives to change as the series goes on. In fact, many readers love this aspect of a crime series – I do myself. But it raises the question – should one read the stories in the chronological order in which they were written? And to complicate matters, some authors write 'prequels'.

I have read many crime series, but very few have I read in the order in which they were written. An exception is Ann Cleeves' books about Jimmy Perez, the Shetland Quartet. And that is a series where, in my opinion (but for reasons I won't explain – no spoilers here!) it is best to read them in order. Often, though, this is a luxury which a reader does not have. What if the early books are out of print (like my early Harry Devlin books), for instance?

As a rule of thumb, I am relaxed about reading a series out of order, and I think most readers should be. But the author's side of the bargain is that it's important to bear new readers in mind even when one is writing, say, book six in a series – one needs to sketch in the backstory, but with great economy, so that spoilers are avoided, and long-time readers do not become bored by repetition.