Great deal for anyone that hasn't tried the game yet.
Here is a quote from the IGN review of the Limited Edition
Most limited or special editions are filled with a few trinkets of questionable worth. This, however, is actually a pretty cool set of goodies, all for just an extra $10. Inside the larger box, you'll find a black DVD case that will make Halo: Reach stand out in your collection. That's a nice touch, but it's only the start.
You'll also find an "artifact bag" that contains notes from Dr. Halsey, the creator of the Spartan program and blueprint for Cortana. This bag is a must for any real Halo fan. Inside a hardbound notebook, you'll get tons of inside info made to look like it was handwritten by the good doctor, a patch, a mock UNSC security badge, a color map and a whole lot more. Play Halo: Reach and then go back and read through the manual for a deeper understanding of what happened in the game.
Last, but not least, you can find a code to get a special armor set for your Elite multiplayer model.
The Halo: Reach Limited Edition package is a great one, and one that I would recommend to anybody that wants more than the base game but can't quite afford the very expensive Legendary Edition. It may smell a bit funky when you first open it (seriously), but it's a great buy for serious Halo fans.