Hi
My reading is not going on well but one book which I read (not worked out completely though) is Understanding Probability by Henk Tijms.
It is perhaps the best book on probability to get started. It is very easy to read and is more application and real life oriented. Standard math books have a theorem layout - proposition followed by proof and repeat. But in this book the author eases the reader into understanding probability concepts right from relative frequency methods which we all know to Markov Chains which Mr Simmons uses (rentech uses a variation called hidden markov as one of the tools).
I think as a market participant we all must know some basic probability and I think if you are on this forum you are well off reading this. Dont get taken aback that it is maths even if you have been a non science student. This book is common sense and I am sure each one of us will understand most of it.
Rgds
Deepak