Help me identify sequels to Verne's books.

I gave an answer to this elsewhere, but I might as well copy what I wrote in case it's useful for someone else:

Regarding the reading order, most of Verne's works are standalones, with the following exceptions:

* Around The Moon (1870) continues the story told in From the Earth to the Moon (1865). It's a direct sequel, starting exactly where the first novel finishes. In fact, we only consider them as two different novels because they were originally published that way, but it would make sense to think of them as a single novel in two volumes. There is a third novel, The Purchase of the North Pole, aka Topsy-Turvy (1889), with most of the same characters, although it's a separate, standalone story.

* The Mysterious Island (1875) is a standalone sequel to In Search of the Castaways (1868) and Twenty Thousand Leagues Under the Seas (1870). It's a sequel only in a very loose way. A couple of characters from those previous novels make appearances in The Mysterious Island. Each of the three novels is a different story and can be read independently, but The Mysterious Island serves to close these characters' arcs. Therefore, if you are going to read all of them, it makes sense to read The Mysterious Island after the others. Twenty Thousand Leagues Under the Seas and In Search of the Castaways are fully independent from each other, so it does not make much difference which you read first. Taken together, these three novels offer one of the greatest experiences that classic adventure fiction can offer.

* Master of the World (1904) is a sequel to Robur the Conqueror (1886). Although Master of the World is a different story, if you are going to read both it would make sense to read them in chronological order, to see the evolution of the character. In any case, in Master of the World, Verne gives a summary of the previous story for background information, when it becomes relevant.

* An Antarctic Mystery, aka The Sphinx of the Ice Realm (1897) is a sequel to Edgar Allan Poe's novel The Narrative of Arthur Gordon Pym of Nantucket (1838) (link). You do not need to read Poe's novel to understand this one, since Verne gives you all the information you need, including a detailed summary when it becomes relevant. However, Poe's novel is worth reading anyway.

* The Castaways of the Flag, aka Second Fatherland (1900) is a sequel to Johann Wyss' novel The Swiss Family Robinson (1812) (link). Again, you do not need to read Wyss' novel to understand this one, since Verne gives you all the information you need, including a detailed summary when it becomes relevant.

Yeah, it was in Reddit. I didn’t delete this thread because I didn’t want to mess up any hidden notifications. Anyway, thank you again!

Exactly! That is the main reason why I created a new one here. 

One of my first Verne books was 'The Mysterious Island,' and I didn’t know it was the last part of a trilogy, so it was quite frustrating.

At that time, I didn't know that it only had a loose connection to the other books, so I was a little bit annoyed. Later, it turned out that it wasn't that big deal.

Yes, I would agree with this, although I read The Mysterious Island before In Search of the Castaways and I don't think I missed out on too much, but I did think it was interesting to see how different Ayrton's personality was in the two different books.