I'm going to post this here because it's a clever trick that I know works - because it worked on me.
There's someone writing as "Laurence Dahners" on Amazon, with a buncha books available. He's got his own website, which is mainly links to the Amazon pages.
There's a variety of subjects, with a kind of "hard sf" backbone to them, without the edgy "check my computations" thing that a lot of hard-sf guys have.
The writing is good, and the editing is good. I still found some errors, including some dumb ones, but they were few and far between.
(My point being, first you need a quality product!)
The idea I want to point out is that at the very last page OF THE STORY - not "of the book", or "of the text", but right at the end of the story, there's a link to the next book on Amazon.
I'm reading the stuff on Amazon's cloud reader, which is to say, their web version of the kindle platform. So when I am RIGHT AT THE END OF THE STORY, going "oh, damn, it's over!" ... there's a link that will take me to the next story, and all I have to do is click "buy now" to keep reading.
It's worth pointing out that this guy has some standard "author's afterword" boilerplate, and occasionally there's a "here's some free chapters from my other book" stuff as well. But those things all come AFTER the end of the story and the link to the next one.
If the "next in series" link wasn't right there at the end of the story, I'd probably miss it. If I didn't miss it, I wouldn't be trying to keep the good feeling of reading the story going, so I wouldn't be as anxious to read on.
Anyway, that's it. If you're publishing for money, steal this guy's good idea: make sure that there's a link to your next-in-series right there after the words "The End." or however you end your stories.
He got me for 14 books so far yesterday and today. (Remember: first have a quality product!)