Where to next?

I’m really enjoying these so far and felt like I haven’t struggled through any of them yet. I’ve finished Horus Rising, False Gods, Galaxy in Flames, Flight of the Eisenstein. I then read Fulgrim, A Thousand Sons and I’ve just finished Prospero Burns. Now I’m wanting to move to other parts of the early Heresy. I was thinking either Scars or The First Heretic, I’m also open to other suggestions, what do you guys think?