Yes, exactly. I've come to have a very low tolerance of books that withhold details in an attempt to build suspense, especially if it's something like a first person narrator who always refers mysteriously to The Incident, when you just KNOW that in fact this narrator is going over The Incident in excruciating detail at least once a day and the only reason it takes five hundred pages to relate to you, the reader, is that the writer is withholding it. Piranesi plays fair: you know just as much as the narrator and indeed can probably fill in a bit more than he can.