Warhammer 40K 5th edition is in wild and in the event you have not picked up your copy yet(You didn't attend a midnight release party?) here is what you are getting:
A close to 300 page book where 2/3 of it is in full color.
About the first 100 pages are the new rules. This is the section which is not in full color. I have not read through everything yet, but it looks like they did a good job of explaining the rules and some of their reasoning for the rules. From the few 5th edition games I have played, I am really liking the new rules. To see some details on the battles, check this out. The one thing missing from this section is a review of what rules have been changed and or removed. I have seen printouts with listings of the major rule changes, but even these are not comprehensive.
The next pages or so are a look into the grim darkness of the 41st Millennium. Each of major races(including the new Daemons) have a section talking a little bit about their history and fighting style. Most of them include a story about a famous battle that faction won.
After the background information, the next 100 pages include detailed hobby information with lots of full color pictures of figures, terrain, and battles. Once again, every race has a section and there is one final section giving an overview of painting and modding figures. Also included in this section is a sample five battle campaign to demonstrate a way to create campaigns.
To finish out the book, GW included the basic stats of all the units in the game. I have been told that some of these stats are the not the same as the ones found in the current run of codices. In a little bit, I will run through both the Tau and Tyranid sections to see if any of those units have changed.
That is about it for this book. With all things considered, this book is worth the $50 and though I cannot say for sure, I think 5th edition will be nice improvement to the universe of Warhammer 40K.