It's the first book we had to read in school that I actually enjoyed. We read it in 7th grade (so we were 12/13 then) Before we had read a couple of random kids/MG-books I found really really boring and I expected to hate 20000 Leagues as well (I was really into Famous Five and similar series where kids solve burglaries or bring back kidnapped animals at that time and so did not expect to enjoy anything that did not involve these sings) but I ended up loving it and developing a great fondness for Jules Verne.