The best cookbooks are the ones that explain why the dish is made in a particular way: the history, the ingredients, and the differences in styles and variations. The Pho Cookbook by Andrea Nguyen is that book for Pho, and it is a page-turner.
Even if you’re not interested in making Pho from scratch, I would still recommend it because it will take you on a fun behind the scenes journey of history and evolution of Pho, key differences in styles (e.g. what is the difference between Hanoi Pho and Saigon Pho?), and give you a new level of appreciation and confidence in your Pho adventures… And, once all is said and done, I would also be surprised if it doesn’t tempt you to attempt it on your own.