Best book to read after TTSS?

I've now read TTSS, seen the 2011 film, and listened to the 1988 radio adaptation. I'll watch the BBC series sometime soon as well, but I'll be reading a book at the same time. Should I jump right to The Honourable Schoolboy, or is there something else one might recommend, and why?

Edit: Thanks to all who commented. I hope your answers will serve to guide future readers as well.