Any suggestions? I'm coming from a math/crypto background.
Not sure about any books, but you might try Hinton's course on Coursera (https://www.coursera.org/course/neuralnets). Not slated to start again for a while, but maybe you can get the videos.
There's also an introduction to them in Coursera's ML class with Andrew Ng, which was an enjoyable and easy intro to Machine Learning in general.
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