It's unlikely that this is the book you're looking for, but a few things fit: Encyclopedia of Chess Wisdom, by Eric Schiller.
432 pages, according to Amazon. Author has a beard. Cover has a picture of the King's Indian. Sadly, I think it doesn't include those biographies you talked about. However, I think the "lost book" could have been printed by the same publisher, as I found another title with a similar cover while searching (it wasn't that one either, since it was shorter).
I borrowed a chess book from my library 8 years ago and I'm hoping someone would know the title of it. I tried looking everywhere online and my city and university's library catalogue but I couldn't find it. It had a black cover and a photograph of a board of the King's Indian Defense (99% sure it was the Sämisch variation but I don't remember). It was a thick book at least 400 pages. It was a book for beginner/intermediate players. It covered everything from openings, middlegame concepts, endings, illustrative games, and a brief biography of every world champion and some of their famous games. I'm pretty sure it was written after Kramnik was the world champion and before Carlsen was the world champion so it was written sometime in the 2000s. I remember it had a section of all the past champions and their nicknames, strengths, and elo according to chess engines at the time. I remember he called Kramnik "iceman" because he was always calm. He mentioned Morphy's was the greatest player in open positions and attacking the uncastled king and that Tal was the greatest at attacking the castled king. I also remember the author had a beard.
I don't expect anyone to know about this book, especially with such little information but I'm hoping there's a chance at least one person would know.