I think reading-order posts should be in-scope if there is reason to assume that there should be an order to read books in.
The easiest case is obviously where all the books are in the same universe. However, that is not the only case. If it can be argued that several books build toward a theme, together, then it's reasonable to assume that there might be a recommended order in which the books should be read. Therefore, I believe that my question about Ayn Rand's stories is in-scope for Literature.
I am not familiar with the works of Thomas Pynchon, but the questionthe question does not tell us why there should be an accepted order in reading his works, and so should be closed not as off-topic, but rather as "unclear what you're asking" or "primarily opinion based." (At least, until a basis for the assumption of a reading order is added. If/when that happens, that post should be reopened.)