I loved the way this was written, a book within a book, two mysteries, and two clever solutions. Always happy to read a murder mystery.

Excellent whodunnit and I also liked the surroundimg Story of Susan Rusland.
I would have given a little bit more intro in the beginning, but overall, it was quite a pleasant read.
The fictional interview of Anthony Horowitz with Alan Conway was a real treat. 

I much preferred the Atticus Pünd story (the "inner" mystery) to the "outer" mystery that wrapped around it about Alan Conway, the author of the Atticus Pünd stories. I didn't much like Susan Ryeland's character voice, and while I didn't guess the whodunnit in either mystery, the behavior of the revealed perpetrator in the "outer" mystery didn't feel in line with their character, which cheapened the whole ending of Susan's story for me.

‘Magpie Murders’ by Anthony Horowitz is a fascinating murder mystery that utilizes books and the murder mystery genre to explore two separate crimes. The frame story in Magpie Murders concerns Susan Ryeland, the editor at a publishing house who edits the novels of a famous murder mystery writer. We get the barest setup of her story before we are introduced to Magpie Murders by Alan Conway, the latest mystery book by the author that she edits. The first half of the book explores, in near its entirety, the fictitious novel Magpie Murders, reverting back to the frame narrative just before the reveal of what truly happens in the fictitious novel to explore a crime surrounding the book and its author. For the second half of the book, the reader is left trying to untangle two mysteries right alongside the main character as she tries to parcel out both the fictitious mystery in Magpie Murders along with the mystery that has sprung up in her own life.
By utilizing the frame narrative, Horowitz weaves an engaging mystery that kept me consistently on the edge of my seat. Though I think both mysteries are fascinating, I think the story within a story in the Magpie Murders by Alan Conway was my favorite of the two. It has a cozy, British mystery feel and because it takes up the first half of the book, I found myself more invested in these characters than I did in the characters from the frame narrative. Even so, I did find the mystery surrounding the book's author interesting as well though I found the solution and situation around it slightly less satisfying than the one in the book itself. 
I do have a few quibbles with this book. For one, there were a few points were it was clear that this was a male writer writing female characters, though a majority of these are in the fictitious Magpie Murders so I’m not sure if these are intentionally placed by Anthony Horowitz to give insight into Alan Conway’s character or if these were just slips on his part. My other issue is with the character of Susan Ryeland. She’s an interesting character for most of the book but towards the end, she makes some big mistakes that seem contrary to how she has been acting in the rest of the novel. Suddenly, she is too trusting and doesn’t think too much about certain situations, where she has been overthinking most of the situations previously. 
Despite this, I think this book was a ton of fun and a very gripping mystery. I highly, highly recommend the audiobook as it uses two different narrators (one for Susan’s story and another for Magpie Murders by Alan Conway) and both do a splendid job. I’m actually kind of sad that all of the books that Alan Conway wrote aren’t real though I am very much looking forward to the sequel to this series. I already have the audiobook on hold. If you like mysteries and are a big fan of books, I think you’ll thoroughly enjoy this novel.