no need to buy anything.
i didn't, i got it all from the inter webs for just the cost of my ISP service
<< this is another example of the lucasarts/disney bringing into canon stuff from legends. you know, so they don't have to think so hard and only need to re organize and 'fine tune' the material others wrote long ago? AKA = "lazy".
they called it all "legends (the EU) and now of been lifting ideas from it for the new trilogy and REBELS, SOLO and Rogue one, hey, its a quicker way to churn stuff out (recycle and save some young screenwriter's brain cells!!!) so why not? >>
again (and again and again and again) i am neutral to highly unimpressed with this new trilogy. i have said it before, but like SOLO, which I have also stated I was not crazy about, I do "get it". I can see what story they are trying to tell based on what has been presented in other format. all of which they have declared canon and all of which is easily found online, for free.
like in this video. you will see where Anakin/DV uses the "world between worlds" to revisit scenes from his past. all the way back to his inception as an embryo.
the world between worlds, what is that, you may ask? well, if one watched REBELS it was introduced there.