For a more casual reader interested in the mathematics and practical applications of GR, I'd recommend Peter Wald's book. It still provides a rigorous introduc

For a more casual reader interested in the mathematics and practical applications of GR, I'd recommend Peter Wald's book. It still provides a rigorous introduction, but has a slower pacing while building up the mathematical foundation of differential geometry. It provides an enjoyable ~150 page read which can be worked through in a few days/weeks if one is comfortable with Calculus. - A Most Incomprehensible Thing: Notes Towards a Very Gentle Introduction to the Mathematics of Relativity https://www.amazon.com/Most-Incomprehensible-Thing-Introduction-Mathematics-ebook-dp-B008JRJ1VK/dp/B008JRJ1VK https://www.amazon.com/Most-Incomprehensible-Thing-Introduct...