There's not that much literature, surprisingly. You can find some basic tutorials on how to create scripts to do basic things, but to my knowledge there are no complete compendium walking through the creation of a complex game like OGame or Travian (two of the most well known) from A to Z.
As far as users, I publicized the games to my friends and on forums where I was an active member, and it was pretty much all word of mouth from there. I never went past 4 digits though.
As for what stops people playing, it's a good question with varied answers. Some people have naturally a short attention span, and move on to other things. Some people just slowly fade away after a few weeks/months because they find another newer game they like better. Some stay for a long time even if they get bored by the game because they like the community. It's very varied.
Ultimately, if you want to keep your players, you need to be active in the community you created: organizing events, communicating with players to solve their problems/questions, adding new features (and publicizing upcoming features they can get excited about); and all of that is very time consuming and hard to do if you're not full time on that project.
As far as users, I publicized the games to my friends and on forums where I was an active member, and it was pretty much all word of mouth from there. I never went past 4 digits though.
As for what stops people playing, it's a good question with varied answers. Some people have naturally a short attention span, and move on to other things. Some people just slowly fade away after a few weeks/months because they find another newer game they like better. Some stay for a long time even if they get bored by the game because they like the community. It's very varied.
Ultimately, if you want to keep your players, you need to be active in the community you created: organizing events, communicating with players to solve their problems/questions, adding new features (and publicizing upcoming features they can get excited about); and all of that is very time consuming and hard to do if you're not full time on that project.