In short, yes it's normal. The flashing is how the screen refreshes itself. You can adjust the settings to make it happen less often.
The reason it happens is that the Kindle - and other ebook readers - use a special kind of screen called E-ink. This is less battery intensive than the screen in a phone or tablet because when you turn the page, it locks the pixels into the words and doesn't change them again until the next page turn. By comparison, an LCD screen refreshes constantly with each refresh reducing your battery life.
You can reduce the frequency of how often the Kindle refreshes the whole page in the settings menu. However you might sometimes then spot artefacts - stray dark pixels left over from words on previous pages - until each full refresh happens.
If you have Page Refresh "Off" (Settings, Reading Options) you'll get the least amount of "blinking". On my Oasis the screen fully refreshes at the start of each new chapter of a book or approximately every 25+ page turns if it's a long chapter.
I don't notice it now as I got used to it very quickly.