I recently read „Journey to the centre of the earth“ and „The ice Sphinx“ by Jules Verne and have to correct the declaration of him being a science-fiction author. He is a very good storyteller, writing adventure books, in the like of Robert L. Stephenson, Daniel Defoe or Dickens. The two mentioned books, as well as his other iconic „80 days“, are stories of adventurers who undertake strenous, never done before journeys during which the most curious things happen and happy endings, all the like. Actually the „Ice Sphinx“ is quite a bold undertaking from Vernes side, as he is writing a sequel to Edgar A. Poes novel „The adventures of Arthus Gordon Pym“, which in my eyes is not that bad.
All this is sprinkled with scientific remarks, so yes, there is a „science“ part here, but it definetly cannot be considered as science-„fiction“ (like e.g. „Frankenstein“ or stuff from H.G. Wells, which try to show the possible outcomes of technological advancements) but rather science-„telling“ in which phenomena are explained with science. But as mentioned, I´d put Verne in the adventure-story part of the bookshelf and considering the very solid, exciting form of storytelling he has, not in the back parts of the shelf.