It seems reasonable to regard Ratzinger’s text as among the most significant works of 20th century Catholic theology, and as destined to enjoy the status of a classic. In my experience, when taught in the right way (I do not claim that my own is the only right way, just a successful one!), it is not too advanced for students at the undergraduate introductory level.

http://churchlife.nd.edu/2018/09/20/a-guide-for-effectively-teaching-ratzingers-introduction-to-christianity-in-theology-101/