After having read a few novels in French, I have been concurrently re-reading my collection of graded readers. Here are my observations.

• Even though my vocabulary is much greater now, and the A1-A2 graded readers feel relatively easy, there are still many gaps in my vocabulary that haven’t been filled. I have learnt that Hachette allow their authors to choose 20% of the vocabulary to suit their story, which may be a reason that there are always many unfamiliar words and expressions. I’m sure other publishers of graded readers have similar rules. (In contrast to that, the rules for the Gnomeville comics are that only the already introduced and defined words are used, plus French-English cognates.)
• As with my previous reading, there are many graded readers that are sufficiently entertaining, but a few stick in my memory. The CLE International adaptation to a vocabulary of 500 words of En Famille by Hector Malot is one that engaged me the most so far. While tastes vary, if you enjoy historical stories about orphans, I thoroughly recommend this one.

One conclusion that I draw from this is that waiting until you know all the vocabulary that occurs in a particular level of graded reader is pointless. You will end up not getting enough practice at more complex grammar. Your interest in the story and whether you know enough to follow the story without being frustrated are your best guides as to whether something is worth reading.