Hi there! We decided to remove the dev book mainly because a) it mentions some things that were poorly worded and could be misconstrued, and b) it has quite a bit of discussion/praise for a celebrity who had a lot of horrible things recently come to light, and we do not want to have any association with (or condone) their awful behavior. Editing the book would require quite a bit of time and rewriting, which we'd rather devote to our new games.
We're very glad to hear you enjoyed RE:H, though! If you'd like to learn more about it outside of the dev book, you could scroll through some of the older posts with the #killhollywood tag on our dev blog. There's quite a bit of discussion of the dev process.