Very rewarding subject. Also one of the most difficult ones I've done. Unlike other applied math units, which tend to be the trivial 'this is the theory, and this is a formula', this subject puts a little more focus understanding the mathematics, such as when certain theorems apply and what conditions are necessary. There are a lot of power expansions, so make sure you like summations and recursive equations and such. The assignments are definitely the hardest I've ever encountered, these are not trivial at all, requires actual thinking, and is very refreshing after years of engineering-esque style of learning.