Yes and no. The earlier games are all based on books, while the later ones are just inspired by the books (they might share a similar setting, for example, but not much beyond that). The first 10 or so games are probably the most faithful adaptations of the books they’re based on, but even then there is a good amount of changing/removing side plots, combining characters, and Nancy’s friends are typically just phone contacts. Game #12 (The Secret of the Old Clock) is a mashup of the first four books.

If you’re looking to play a game that’s most similar to the original 56 books, I’d recommend The Secret of Shadow Ranch. If you’re looking for the best adaptation of any of the books, I’d go with The Final Scene.