[.ca] An Introduction to the Invertebrates (ISBN 0521857368)

is what it says it is:
Moore's introduction is brief, but informative. Structured in the standard format for a zoology textbook, she covers the basics quickly and well, and then raises interesting questions that pertain to whatever phylum is in question. Having already done coursework in invertebrates, I found this a good refresher and still full of things I did not know (or had completely forgotten).