Lie Theory

Below is a list of reviews of books on Lie theory.

Naive Lie Theory
Stillwell, J. (2008). ISBN 9780387782140.
As the title suggests this is an introduction to Lie theory with minimal background requirements: linear algebra and some calculus.

The classical Lie groups are introduced as rotations in two, three and four dimensions with a lots of appeal to geometric imagination, before discussing them in more general settings. While other books on the topic rely on heavy theory rather quickly, this book presents a more elementary approach and makes this fascinating topic accessible to undergrads.