kindles are waterproof now, they are much easier on the eyes while reading than a backlit device such as an ipad. They dont do internet as such. if you do/are oing to be doing a lot of reading then get a kindle
The Kindle app is available for most mobiles and Apple have the Books app, but I use free ebooks on my iphone via my local library using the Borrowbox app.
Two sorts of Kindle - Fire and Paperwhite. Paperwhite is just a reader for books bought/rented from Amazon; Fire can read books from public libraries but are not good in daylight.
Kobo is an alternative - it's like the paperwhite but can read public library books.
Paperwhite and Kobo have a much longer battery life than Fires because they are simply readers, not tablets.
My information might be out-of-date, as I haven't bought a new one for a couple of years, but the principles still apply to the capabilities of both makes.
I have got a kindle and an iphone and ipad. The iphone is much too small for me to read books on and, while I love my ipad, it is heavy to hold. The kindle (I have a paperwhite) is just right. its compact and light enough to be easy to hold and carry with me and the screen is better in sunshine.
I have both sorts still prefer my paperwhite for reading. Huge battery life about two weeks for me, ordinary fire for everything else. Recently upgraded to a bigger fire but still hard on eyes but you do get the benefit of the colour screen for illustrations.
I have used my ipad for reading on the kindle app from time to time, but find it gives me eye strain if I read for too long on it. I also have the kindle voyage and use this most of the time, wonderful so easy to use especially if you read in bed. I would love the Kindle Oasis which has the bigger screen but it is a bit expensive for me and would only upgrade if my kindle voyage started to go wrong. I believe it is to do with the lighting on the ipad which is not so easy on the eyes compared with the kindle voyage which is specifically designed for reading.
I have an iPhone, iPad and Kindle and get good use out of all three, as would you tinks if you do a lot of reading. Kindles are small, light, thin, long battery life and built for reading for long stretches at a time.
Given I have an iPhone and iPad I wouldn't get much use out of a Kindle Fire, which is more like a iPad competitor. Don't confuse a Kindle with a Kindle Fire.
I love my Kindle paperwhite and couldn't be without it. It will sychronize with your iphone and ipad if needs be ( waiting at the dentist a long time and didn't bring the kindle) but Kindle is best. I tried reading a "real" book again a few months back, as I was clearing them out and found some old favourites, but it's no good now, can't hold them comfortably. Long Live the Kindle !
I have a backlit kobo ereader which I could not do without. It is very light and fits into a pocket, the battery lasts for weeks.
I get my ebooks for free from the public libraries and BookBub and buy them from anywhere including Kobo, Google Play and Amazon (the Amazon ebooks need converting). It is very comfortable to read anywhere.
I have an iPad, an android tablet and a smartphone all with the Kindle app but find the reading experience much better on my Kobo because it is so much lighter and doesn't strain the eyes. Less distraction and less charging.
I will not buy a Kindle as I don't want to be tied to Amazon for my eBooks.