In preparation for the upcoming season of Game of Thrones, I purchased this rather large tome from Martin, along with Elio Garcia Jr. & Linda Antonsson (the people behind A Wiki of Ice and Fire). It is, unquestionably, worth the investment.
This is not a new novel in the Game of Thrones world, but can be thought of as an encyclopedia of pretty much anything related to this world. Have a question on Naath, the home of Missandei? Look it up here. Always wanted to know more about the Fingers, where Petyr Baelish is from? This book has you covered.
The first section of the book deals with history, from the Dawn Age up through Robert’s Rebellion (the skip over many era where there is not much documentation). After that, they delve into a great amount of detail on each of the different areas in Westeros, then Essos.
In truth, there is not much difference in information between what is collected here and what is available on A Wiki of Ice and Fire, but there are some places where there is a bit more detail but what sold me on buying the book was the artwork. There are gorgeous illustrations throughout including a two page rendering of the Iron Throne (which looks much different than in the show), the battle between Robert and Rhaegar and various pictures of Aegon riding on Balerion the Dread. Plus, I find it easier to look stuff up in a book when I am watching the show rather than to search for it online.
This book is an incredible resource for anyone who wants to delve in deeper to the world Martin created and if you, like me, sometimes say to yourself when watching Game of Thrones, “wait, who was that again? Or how is this guy related to this other person?” Then picking up The World of Ice and Fire can help ease some confusion