It's impossible to say what "would happen", but the worst case scenario is that you would end up losing books that you paid for and perhaps have a device that is no longer usable for your intended purpose. Technology is advancing very quickly these days, and that brings with it the possibility of both good and bad results. If the convenience it brings is worth the risk/cost to you, that's fine. It's not worth it to me, therefore I don't need or want an ereader or a tablet.

What Amazon does is keeps every book you purchase from them in your library at Amazon in your account, but to read the books you must download them to the reader first, so then you will have the copy on your reader and at your account. That is the only way you can be able to read while not connected to Amazon of course. Should you need to get your book from the account page you can, if say you and a spouse both have ereaders and you want to share your Amazon account then the books in your Amazon account can be used by both readers but you must only have the one same Amazon account for both.
My brother in law has an account his wife has a reader she shares his Amazon account she can have access to all of his books on his Amazon account.

On most other type readers you get your books from where ever you choose you download them either directly to your reader or you download them to your pc and put them on an SD memory card which you can then put into your reader if your reader takes SD cards which most Android readers do.

Has it happened that Amazon closed someones account and they no longer had access to all the books they had purchased and owned yes it does happen it is in the terms of agreement. Not fair at all in my opinion since you have paid for those books. So best practice if you buy them download them and keep your own copy!

luis-
I don't think you should be concerned. Even if a hacker were able to cause problems to Amazon's cloud services, it wouldn't affect any books you had on your eReader, and it wouldn't cause any longterm problems if you had to download the books again. Second, don't worry about poor Amazon going broke...their stock has gone up by a factor of 5 in less than three years, and a majority of analysts still consider it a "Buy." Overall they are quite strong and the money they are intentionally losing by pricing Kindles low is like the razor manufacturers: you get a great deal on the razor and they more than make it up on the blades you have to buy later.

"So best practice if you buy them download them and keep your own copy!"

You mean keep a copy of the book on a pc? Meaning there is a way to copy books from all ereaders into a pc?

Those that use an sd card yes for sure and some allow you to transfer between pc and tablet via usb cables . But depending on where you are downloading the book from you can either download it directly to the pc or ereader, and of course depending on the ereader. Amazon is pretty restrictive in some ways. Other android tablets not so much.
I personally do have a copy of all my books on my pc, then I can put which ever I want on sd and put it into the tablet I am using at the moment.
I have the kindle app on all the tablets and computers so any kindle format books I can read from any of these. I used my one amazon account on each device so I can access my Amazon library with all and download my books to any or all of them.

I pretty much manage my ebooks like ravencajun, but I don't even use cables. I usually will just email the file from one device to another, and use the wonderful and free Calibre program to change formats if needed.

Yes if it is a tablet that you can email from you can do that too, I have done that a time or two. And most tablets allow you to move things from the device to the Sd card. In fact many apps can be moved to the sd card to help keep your internal memory freed up.
I use an app that does that easily called app to sd.

I received the Kindle Touch as a gift last Christmas. I have several books for it. I got them all from amazon and they are all stored in a folder on my PC, on my Kindle and I guess they are in the cloud somewhere. I can disconnect my kindle or PC from the internet and still am able to read the books so they are on the device. I did not take any steps to store them there. I just clicked on the link to buy them at Amazon and they were stored automatically. I guess they are on the PC because I ordered from the PC, not from the Kindle. I have a folder there called My Kindle Content. It may have been there before I got the Kindle Touch because I had Kindle for PC on the PC.

I have a kindle keyboard and a kindle fire. Books and apps you download are all stored in your amazon account. That is one thing I love about my kindle. I don't have to keep everything stored on my device. If I delete something from my device I can just reload it from my account. If I am traveling and want to reload I just stop where there is free wifi. If you delete from your account then it's gone for good and you would have to buy it again. I have had my kindles a few years and never one bit of trouble with my amazon account. I did a lot of research and for me the kindle was the best fit. Mary

O.K. Slow to catch this bus - I don't have an ereader but would like to have one. How do I determine which to buy? Why do 'they' say download books for free, books are free, etc. yet reading people's remarks they talk about buying books from Amazon? Would someone enlighten me on the world of ebooks & ereaders? Would definitely want one that was non-glare because I love to read on my back porch facing the water - lots of glare.
Info & maybe your experience please? Thank you.

I apologize - I didn't mean to hijack this original question.I should have started a new thread but I haven't been on GW in so long I forgot that. I tried to go back & delete the above response but there doesn't seem to be a way to do that.

I have an amazon kindle e-ink reader and 2 kindle fires. Amazon does offer some books for free but most newer popular books you buy just like you would at a book store. Amazon does offer kindle unlimited now. For $9.99 a month you can borrow up to 10 books at a time. Also most libraries have e-book lending now. You will have to research and see what reader meets your needs. Mary

Also if you want to read in the sun you will want an e-ink one. The kindle fires are backlit just like a tablet or cell phone and can't see the screen good in bright sunlight. The amazon e-ink readers are just for reading and don't do apps for games and such like the kindle fire tablets.

Some of the amazon e-ink ones come with free 3g so you can download books any where with no WiFi conneconnection. If you get one that is WiFi only then you will have to find a wireless connection to download. Wireless in your house, McDonalds and such, where ever there is free WiFi if you don't have a wireless set up at home. Mary

Thanks Mary - that's a lot of good information.

sanantoniorose,
I have read some very good free books by subscribing to a website called Pixel of Ink. They will send you a list of books (and a number of them are free) daily via email.

Here is a link that might be useful: Pixel Of Ink

My E-reader has a 2GB SD card and holds hundreds of books, but then I only upload Free books and do not pay or use Amazon etc. to acquire my books. So I have them forever if I choose to keep them.

I have them for ever also. They are permanently stored in my amazon account, same with apps. If my device dies I just register the new one to my amazon account or the reading app I can put onto another brand tablet and all my books and apps show up for downloading. About 80% of the books I have in my amazon account were free from amazon so between that and the public library I don't spend a lot. Mary