There's tons, if you look up "[language] graded reader" or "[language] nature method."
Familia Romana by Hans Orberg is a great one for Latin. I frequently see people call it the gold standard for this kind of book, but they're all Latin enthusiasts, so they're not exactly unbiased.
I didn’t find that many - you can find graded readers, but very few ‘graded novels’ ( as in a full novel where chapters are progressively harder, not multiple independent tiny stories ) if I may say so
Familia Romana by Hans Orberg is a great one for Latin. I frequently see people call it the gold standard for this kind of book, but they're all Latin enthusiasts, so they're not exactly unbiased.