In Italian, 'detective novel' is typically 'romanzo d'indagine'. However, depending on the specific context or style of the writing, 'romanzo poliziesco' or 'romanzo giallo' could also be appropriate.
You can say 'non-fiction' in Italian as 'saggistica'. It's used to describe various types of non-fiction literature like biographies, history books, and more.
The way to say 'detective novel' in Spanish is 'novela de investigaci贸n'. It conveys the idea of a story involving detective work and mystery-solving. So, if you want to talk about this type of book in Spanish, you can use this phrase.