This probably should be a four-star(-plus) rating because the stats section was a bit underwhelming and felt a bit rushed—the LaTeX formatting, too, was a bit unwieldily and inelegant in various spots—but I "rounded up" due to the wonderful chapters on probability, the quality of the examples/test cases, the clear exposition, and the proofs. I've read Rosanov and a bunch of other texts on probability theory, but Larsen and Marx's tome does more than enough to make room for itself. I can't remember the last time I read a textbook where the marriage between theory and practice was so effective, immediate, entertaining, and illuminating. This is an achievement.
Yes, you need the (basic elements of the) machinery of calculus to understand what's happening in the first 2/3 of the book, but its inaccessibility to beginners and casual readers is counterbalanced by what it offers those prepared to engage the material. If you're interested in the mathematics of probability (or you're taking stats with a heavy probability component), this would be a fine companion text to supplement your learning.