In short, the best advice I can offer you is to read the books in whatever order seems best to you. More generally, all of the books include passages in which Roland reminisces about the past and tells stories about what the world was like before it 'moved on'.

For example, most of book IV ( Wizard and Glass) takes place in Roland's childhood some of the events of book VIII ( The Wind Through the Keyhole) take place between the end of book IV and the beginning of book V, but the main story is also set in Roland's youth. The books of the Dark Tower series tend to jump back and forth between different timelines and the chronology is not particularly consistent. I imagine that many people would recommend reading the secondary stuff first, then starting on the Dark Tower books, comics, etc, but really, it doesn't make much difference. The order in which you read the books is ultimately up to you as the reader. You won't miss many important points if you don't read any of these books, but they do help to provide some background information that enriches the story of the actual Dark Tower series. In my own personal opinion, of the secondary books that I have read ( It, Insomnia, Misery, The Dead Zone, 'Salem's Lot, Eyes of the Dragon, Firestarter, The Long Walk, The Stand), it seems that the most important ones are as follows: It would be incredibly difficult and time consuming to read all of the related secondary works - that list includes the majority of King's books: It, Insomnia, The Stand, 'Salem's Lot, Hearts in Atlantis, The Mist, The Eyes of the Dragon, Everything's Eventual, Rose Madder, The Talisman, From a Buick 8, Firestarter, Dreamcatcher, Cujo, The Long Walk, Misery, The Dead Zone, and many, many more. You can then move on to the comics and the short story about the Little Sisters of Eluria. I would suggest that you read the actual Dark Tower books in the order in which they were published.

Wolves of the calla