I have no interest in writing mysteries, but I was interested in reading about how they were put together. This book is as excellent as it was disappointing. You need to take it chapter by chapter. The first half of the book is fantastic. Beinhart puts a lot of wisdom and savvy into those chapters. However, sometime during the third fourth of the book, his narration style became casual. The subject matter wasn't covered as completely, or with the same finesse as earlier. In fact, he insulted several peers. Worse, the examples he used of other writers' works often didn't support the point he was making. It reminded me of a friend of mine who can't tell funny stories because he spends more energy laughing than describing what is actually funny. Whatever point Beinhart had in his mind when he shared the quotes stayed there. The final fourth of the book began to disappoint me. The chapter on Cozies was horrible, showcasing his naked bias against them. Fortunately, he included statements from several authors who made their livings writing cozies, so there was something to be learned there. The final fourth was redeemed in part by the chapter on receiving criticism from beta readers, then sealed as priceless when he included a step-by-step process of how he brainstorms a book. Any new writer could benefit from that chapter regardless of their preferred genre.
I should mention that there were archaic references throughout that dated the book, like the section on self-promotion that referenced CompuServe forums. There were also two unnecessary uses of the n-word which might be excused as being from an earlier time, but since Beinhart lives in England and the book was originally written in 1996, I suspect he was just used to having conversations with his low-life characters.
In the end, I found the book uneven, but filled with useful information. It's better read by subject as opposed to being read cover to cover.