GENERALLY SPEAKING.
A well designed installment inn a series (e.g. Game 1, Game 2, Game 3, Book 1, Book 2, etc) should actually be a standalone product. Connections are fine, but you should, in general, avoid having the previous material be absolutely required for the enjoyment of the current material. Otherwise, you risk alienating players/readers/etc. In addition, it is generally just poor design. Any individual installment should be a complete, self-contained work.
Now, as the other side of this. Each installment should also be enchanced by the installments around it as well, otherwise having the other installments is as silly as having several installments that cannot be understood unless you put them in together.
So, while it sounds a bit silly? It isn't really isn't as silly as it sounds.