Scribd is pretty terrible for longer stuff. I have posted a few shorter pieces up there int he early day, and still get hits on them, which is neat. But whenever I have tried to download something from them, I wind up with a disaster of a file without proper line breaks etc. that is totally unreadable on all of my devices.
Since you say you want an 'education' from readers in how they buy/read books, I'll just share fwiw my path for ebook buying/reading and why.
IF IT'S A FREE/PUBLIC DOMAIN BOOK
First stop is this forum. The books here are manually formatted to look optimal for my Sony, so this is my preferred first stop.
Second stop is Feedbooks, if the book isn't here. The custom PDF for the Sony looks very nice. I also appreciate that short stories are available as stand-alone works. There was one by Doctorow I really liked and I didn't need the whole book, just that one story. I also like that you can rate books and get recommendations. I just wish there was a way to filter out all the comic books and short stories to only show the novels...
Third stop is Manybooks.net. It's a little more 'serviceable.' The files are readable, but are not as pretty. They do have quite a few that my other sources did not have, though. The selection is very extensive, especially for genres like poetry.
FOR PURCHASED BOOKS
Fictionwise has thus far been my one and only stop. I like the multi-format books because there is no DRM so I can download them in whatever format I want/need. I do buy the secure eReader books if it's a massive sale and/or something I really want and/or it's at 100% rebate. But it's a bit of a labour-intensive process to both remove the DRM and also convert the resulting badly made HTML file into something decent-looking to read, so I find that my purchasing of such books since I got my Sony has been VASTLY reduced. I read fast; they would sell a lot more books if they did not have the DRM on them!
I have checked out Books on Board but hate the way their site browses. Also, I am invested in the Fictionwise reward system and use the credit on my rare DRM purchase to buy whole bunches of other non-DRM purchases
So I am not interested in getting into another big store.
BUT...
With that said...
eReader.com has new lower prices with no book over $12.95, and that has put them on my radar. I have not bought from them yet but I may in the future.
And Smashwords is starting to interest me more. I like that you can, in most cases, sample portions of the book for free first to make sure you'll like it. However, most of the authors there are not ones I am familiar with so for me, I would not go there so much to browse (yet) but if I knew about a book specifically, I might go there to get it.
Individual author websites don't really interest me. I would rather have the one-stop shopping of something like Fictionwise and the security of being able to download the book from them again if the need arises.