As many E-Book readers know, E-Books do not have pages like PDF documents. On the other hand, you need pages or page breaks to create choose your own adventure books (let's say CYOA). Also, you need links (navigations, bridges) to other pages.
Firstly, to create E-Book with the epub format, I used google docs.
File -> Download -> EPUB publication (.epub)
After downloaded the epub file, I edited the book with Calibre.
To create a page break I used the code below.
<span style="page-break-after: always" />
To link other pages for CYOA choices firstly you need to put id tag beginning of the page like below.
<h4 id="page2">Sayfa 2</h4>
And you need to define your link to the page as below.
<a href="#page2">Sevda Öğretmenle grup değişikliğini konuşacaksan (sayfa 2’ye)</a>