I feel the following sentence would be used by Native speakers but only in highly informal speech in certain areas:
In his letter he explains how the book has a great plot and is generally enjoyable.
I checked When to use the words "how" and "that" where the phrase "he thought about how ..." is discussed. The answer there states that "How" has been in widespread usage in this way for years, so even if it is not formally correct, it is widely accepted.
I feel that this is not the case for my example. I believe my sentence would rather be seen as wrong or inappropriate in a more formal context (e.g. essay). Is that correct?