This is really good news, I'm not particularly interested in reading any of his "non Bernie" books, and I had feared that Philip somehow thought that Bernie was " holding back his creative juices."
I'd like to read prequels to the series too- I'm not sure how much into the 1950's this can go and remain interesting but it can certaily go backwards into the 20's.
I found that A quiet flame was most the most upsetting, the thought of jews escaping from Europe and then being treated like that was awful. I am re-reading the whole series of books again, and it still manages to discomfort me.