The best way to read the AOT manga is to get it in a format that suits you, like physical copies or digital. Make sure you have a clear understanding of the characters and the world-building. Read at your own pace, pausing to think about the plot developments and enjoying the art style.
You can start by finding a reliable source to access the manga, like official manga apps or websites. Then, just start from the first chapter and follow the panels and text to understand the story.
I'm not sure exactly, but there are quite a few volumes of the Attack on Titan manga. You might want to check reliable sources or the official publisher for the precise count.
The AOT manga has finished. It wrapped up all the major plotlines and provided a conclusion to the story that fans have been following for a long time.