I was thinking about the Beatles the other day. Bear with me, it's probably a bit of an age thing; I'm nearly 50 and the Beatles were just... there all the way through my life. Up to and including that time when Paul McCartney seriously narked me by stealing the news coverage I had planned for my dance team (if you want that story, say so. It involves the Evening Standard, some undignified scuffling and a prat in a box).
The thing about the Beatles - and the Stones, as well, really - is that, in the course of their artistic careers, they were allowed to change, and change dramatically. If you listen to something like She Loves You and follow it almost immediately with Blue Jay Way or Within You Without You (or, for the Stones fan, compare Satisfaction with Emotional Rescue) you struggle a bit to remember that you're listening to the same band. Whereas if you took the first Oasis album and the last one and stuck the two on shuffle, anyone who wasn't fairly dedicated to the band would probably struggle to say which track came from which album and not from any of the ones in between.
Nowadays, nearly any band that gets listened to widely for more than a couple of years' worth of music-producing seems to produce nothing more than slightly-twiddled versions of the hit single and the not-quite-such-a-hit single, over and over again. If you started out as Goths, Goths you must remain - coming up with a bit of ska or Britpop or classic disco will get you nothing more than a smack on the head from the record company. If you want to do something a bit different to the Thing You Do, you have to run off and do it in your own time, usually with someone other than your regular bandmates, and you often have to give yourself a different name.
Similar restrictions seem to apply to writers, as this blogpost from erotic writer Janine Ashbless shows. It seems to apply in particular to writers of erotic material - as recently as 1996 a how-to manual was advising authors to have a 'separate pen name' for their filth, though this was more on the grounds that writing about sex in an enjoyable, arousing way was something you were supposed to fence off from your 'proper' writing. But the current trend seems to be that if you write erotica, you're supposed to stay in a little tiny box appropriate to the type of erotica you write. So if your first widely-read book featured predominantly BDSM, or LGBT, if you want to write about spanking or polyamory, you need to change your pen name. And if you have sold a few books under the branding banner of 'hot romance' and you want to add a bit more group sex or fisting to your next one, it's better to give yourself a new identity, or your regular readers will shit the bed and pass out.
What irritates me is that I don't actually think the majority of people who like to read books *are* this stupid and stubborn. I think that (again, particularly with regard to erotica) a lot of the publishers are the ones who think the readers are dimwits who have to be peddled the same thing over and over again, and that people who read books - and come on, readers are basically the top of the food chain - are quite capable of enjoying something that isn't just the same as the last thing they read.