It is your choice. Although I would personally recommend reading the whole manga, there is no problem picking up from where the anime ended. You don't have to listen to all the manga elitists who try so hard to make the anime look worse that it was in fact. Chapter 59 is when they decide to go after Kaneki. I think this is the best point for an anime watcher to start the manga, as things start to differ majorly from this point onwards.