I started not knowing a "put" from a "call," but I needed to know a fair bit about how financial engineers (coming from a family of PEs, I'm still not used to that term) use math. This has been the introduction I wanted - not the advanced stuff, but enough to help me understand that material.
Methodical pacing leads the reader gradually through the basics, from just what a derivative is on through the brief story of how futures markets work - in short, they abstract buying and selling into buying and selling the right to buy and sell. I tend towards the concrete, so many of these transactions seemed a bit airy to me. Oh, I can follow the reasoning well enough, but I just never saw where the satisfaction of the thing solid and completed comes in. As it turns out, it doesn't. Once you've really got that in the pit of your stomach, then Hull's presentation follows smoothly.
He gradually derives models of increasing complexity. Diligent reader with a little calculus or a lot of trust will follow along easily. Later chapters draw on more advanced concepts in probabilistic modeling, but present the reader with only the aspects needed for the discussion at hand - a mercy, considering the size of the specialized vocabulary involved in the rest of the explanation.
This book ends when the foundation has been built. More advanced needs must be met with other sources - not a problem with this text, just a matter of its chosen scope. I needed that foundation, however, so I recommend this book to anyone with reasonaable math skills and a need to know the material.
-- wiredweird, reviewing the 6th edition