Hi Celialemos,
I use an iPad and am quite happy with it. Several things you might want to think about. Keeping your hands clean and dry-physical books can take a splash, but electronics can't. Either have lots of hand towels around and get very good about drying your hands or get a waterproof pouch (check out Amazon). Don't plan on leaving your tablet plugged in unless you don't mind killing the battery early. And you may want your battery. One of the great things about a tablet is the portable nature of your books. You can sit on the sofa and read any book in your library. You can also take it along if you will be waiting in line somewhere. Even sitting in your kitchen with a cup of tea and flipping thru the pages, just as you would with a print book.
Set your sleep settings with cooking in mind, so that you don't have to unlock your tablet multiple times. Treat security seriously, either logging out of amazon after a purchase or having a locking code on your tablet and being sure it is locked when you are done.
Screen size is pretty personal. My present tablet is 10.5". We have a 13" at our veterinary hospital and find the screen size useful but the tablet itself too large to handle comfortably. Beautiful, though, if you don't plan to have to handle it. We keep it propped on a desk for easy access. I personally don't like the smaller tablets for cookbooks or embroidery books. Great for fiction, but not enough screen space to adequately look at recipes or books where illustrations matter.
You can buy cases with keyboards attached. Again, pretty personal. I feel that an attached keyboard detracts from the portable nature of a tablet. My husband adores the keyboard and requires on for every tablet. If I need to do a lot of typing, I use a computer rather than a tablet.
Lastly, if you think epub cookbooks are likely to be your future, get as large a memory as you can afford. Cookbooks tend to be larger than fiction books and fill a memory more quickly. Since your plan is to use the tablet as a bookshelf and not as a gaming device, long practical lifetime is more important than the ability to upgrade to the latest and fastest. My son has a 12yr old iPad that he uses to access the web. We keep an 8 year old version down on our bar, complete with various drinks books and some grand drink apps. Not something that needs a lot of processing power, so they just need to keep powering on. Both were replaced for inadequate memory. I am a slow learner (grin)
Zephy