I don't actually read very many mysteries, but whenever I do, I remember just how awesome they are. It's kind of neat to have everything slowly unveil before you as the main character figures everything out. :D Dead Letter Office definitely did the whole mystery element well, and the fact that it is an active fiction title made it even better! Instead of being a passive reader experiencing everything as the character makes choices, you get to make the choices for them and that was fantastic! 
 I made sure to read all of the possible alternatives so that I could review this title fairly, and I really liked that the differences between paths were subtle, but they also stood out and did take the story in different directions. :D I definitely loved that you get to choose how it all unfolds though because that was a really interesting experience. :) 
 Along with the mystery element, Dead Letter Office was also shrouded in the paranormal, and since the main character, Celia, was pretty curious, she worked hard to try and figure out everything that's going on. I really enjoyed Celia! She was curious, and I liked the honest relationship she had with her mother. :D Donovan, Tilly, and Luc were also really interesting characters. I'm gonna try to spoil too much, but there is definitely a love triangle going on in this one...and boy is it a strange one. :P haha I loved that each character provided a different element to the story through their relationship with Celia, too. Through Donovan, you get to see the whole Detective side of uncovering the truth, and through Tilly, you get to see magic and all that fun stuff! :D Luc also brings a very interesting perspective, but I'm going to let him remain a mystery until you read Dead Letter Office yourself! ;D 
 Overall, I loved Dead Letter Office! The active fiction aspect of the story brought a whole new element to the story, and made the mystery even more fascinating. The characters were great, and the writing was descriptive and kept me riveted until the last page...in every version of the story that I tried! I'd recommend this one to mystery fans, and even to those who aren't a fan of mysteries. I think you'd really enjoy this one if you like crime stories on TV, too. All in all, I thought Dead Letter Office was fantastic, and I can't wait to read the sequel, Post Mortem! :D