I got a bunch of the Horus Heresy books at a locak half price book store. #'s 2 and 3 are missing but I have the rest of the serries to date from this purchase. Do I need to read the ones I am missing before moving on to the 4th book? Some serries it is huge if you skip others it is like missing 3 years of soap operas where nothing has happened since they spend a lot of time doing flashbacks and reviews or previews.