As of now, I don't know the specific name of the novel on which 'Knives Out' is based. There could be various reasons for this, such as it being a relatively new or not - so - well - known novel that hasn't received as much mainstream attention in relation to the movie.
Well, 'Knives Out' has some roots in real - life scenarios. You know, in the real world, there are often disputes over family wealth, just like in the movie. However, it's not a factual account of a single event. The director has drawn inspiration from the general idea of family feuds and the chaos that can ensue when there's a lot at stake, like an inheritance. So, in a sense, it's based on a 'true story' in a very broad way.
Yes, 'Knives Out' was inspired by real - life mystery stories and the classic whodunit genre. The filmmakers took elements from various mystery tales and created their own unique story within that framework.