You can find all kinds of advice on writing ebooks, but you have to choose what's best for you. Some people make writing ebooks sound so easy and say you can make lots of money. Perhaps it is easy for some writers, but I didn't think so. It took me three months to compile information and put it together into a book, and then I spent even more time editing. Then after my book was published, I had to learn about promoting it - a book doesn't just sell by itself.
I decided to write my first ebook for Amazon since I discovered you don't actually have to own a Kindle to read their books (I don't own one). Amazon offers a free cloud reader, which may encourage people to buy even if they don't have an e-reader.
Even when you publish your book on Amazon, you still own the copyright, so you can also publish it on Barnes and Noble, Kobe, Apple, and other places. I plan to investigate these options later on.
Writing an ebook allows a person to write a book and get it published immediately, although your book still needs to be good or no one will buy it. You also need to write about a topic other people are interested in. I hope people like my first ebook, but if not, I'll learn from the process.