Roughly translated here -
Krone - Did you want Book of Souls to have a concept?
Bruce - No, this is not a concept album. Take the first song, IESF. That was completely written for a solo album of mine. I had 5 demos that were of interest to Steve and 2 from those could have been used for Maiden and one was IESF. The other song came from the Accident of Birth sessions. It was called "Nightmares" and was never recorded for the album. That one, however, was co-written by Roy Z so it could not be used for The Book of Souls. IESF is entirely my piece though and it's about a foreign machine that steals souls of men. The evil man in the tale is Dr. Necropolis and the good Professor Lazarus. They are in the spoken words near the end. Steve wanted the song for Maiden and I agreed but he wanted it to be longer. So I wrote an extra verse. It's the only song done in drop D.
That's the gist anyway.