There are many excellent reviews here, and because I'm neither a mathematician nor a physicist there is little I can add. But for those like me who are smart, curious, and patient and who are wondering whether to have a go at this book, I say go for it. By the time you have labored your way to the end, you'll find that you have absorbed far more than you expected. When Penrose is not doing math, his voice and his prose are crystal clear. If Penrose loses you, sometimes taking a look at, say, the Wikipedia article on a particular subject will catch you up. If gaining a better understanding of physics is a longterm goal for you, then this book is a valuable reference.