Rise of the Dragon is an illustrated and condensed version of the novel Fire & Blood, detailing the history of the Targaryen rule of the 7 kingdoms in the Game of Thrones universe created by George R.R. Martin. It is the primary source material for the Game of Thrones prequel series, House of the Dragon. In fact, if you have watched the first season of House of the Dragon, that story appears about halfway through this book. This book will, in broad strokes, spoil what is likely to be the ending of that series (depending on at what point in the story the showrunners decide to end the series), as it outlines what will come next. Given that the book did not include all of the details that we saw in the first season of the show, it is not likely to spoil everything that will be seen in the show, but you will get an idea of where the story will go. This is probably the first of what will be at least two books, as this one ends before the events of Danyeres' father's rule and his downfall.
The hardcover version of the book is 342 pages, a lot of which are illustrations. As was the case with the book Fire & Blood, it can be hard to keep all of the characters straight, especially since many of the Targareyn characters have similar-sounding names, and names get reused over and over. Having illustrations that show some of the scenes that are being described in the text does help a little bit, but it definitely makes this a slower reading book than it would normally be.
The book is very good, and the illustrations are great. Of course, many of us would prefer that Martin focus his time and energy on actually finishing the final two books of the Game of Thrones story, but the reality is that he is going to jump around from project to project and he seems content to finish GoT in his own good time. One good thing about this story being mostly finished is that the House of Dragon TV series will have a clear guidepost for where it is going whereas the later seasons of GoT did not, which will hopefully allow that series to end in a more satisfying manner.