I have to preface my review by saying that if you're planning an extended trip (more than 3 nights) to any of the cities that this guide focuses on, you need to purchase a guide for that specific city/area.
That said, Essential USA is great if you're the type of person who likes long weekends away. It includes just enough information about some of America's greatest cities to give you a taste of these places, but again, if you plan on taking a four+ day vacation to, say, New Orleans - buy a New Orleans guidebook. Also, the Las Vegas section was especially devoid of quality information, which was disappointing.
One of the best things about this guide is the road trip ideas! It gives you some great itineraries, so if you're not one for simple long weekend trips this would still be a good purchase.