This book contains the most useful, flexible and powerful RPG system I have ever had the privilege of learning in the 20+ years I've been playing tabletop RPG games. For the games I run, this system allows me to create the world I envision.
In almost every case, the game you run will be heavily colored by the system in which you play it, be it your own home-brew game rules or a published set. This often feels constraining, forcing story tellers to place artificial limits on the stories we tell. Legends of Anglerre provides a balanced, innovative way to use the open-source Fate system for a fantasy setting. In my opinion, it does this very well.
The game does not sacrifice believability and balance for this increased flexibility, however. Further, it places more responsibility for telling good stories in the hands of the players -- reducing boredom at the table during times when other systems will drag (combat in many fantasy RPGs comes to mind as something that tends to drag and leave players bored while waiting for their turn). If you have players that love to tell stories together rather than play tactical war games, Legends of Anglerre might be the game for you.
As a practical example, my gaming group and I played using DnD 4th Ed. This is a fun system in its own right and I like the balance it brought to DnD. However, if like me you've only got 3 to 4 hours to get together with your friends and play, then you are likely to run into the same problem I had. That is, trying to fit in good role play and storytelling and anything more than one single encounter in that time is nearly impossible. Progress crawls. People sit at the table bored while their friend tries to figure out which power is tactically the "best" thing to do right now. While fine for sessions of 5 or 6 hours, this just wasn't going to work for my group and I anymore. So, we switched to FATE using this book, and we have regretted nothing. Same world (my own making), same characters with the same concepts and strengths. Only now everyone has something to do, we can run through 4 or 5 encounters in an evening's play and we're telling amazing stories as we do it!