I reviewed this a while back and really enjoyed it. I don't know that it's necessarily the best place to start reading the series, since it refers to quite a few things that happened in Book 2, but it might give you an idea if you'd like the author's style. Prior to Claverton putting this up on Smashwords, the only way you could get it was by signing up for her newsletter.

And yes, I know the title on Smashwords says Captcha Thief, but I think the author was just getting her wires crossed and hasn't caught the mistake yet, because Captcha Thief is the third book in the series, due to be released by a small press in a few months. Somehow I doubt she'd be releasing that for free.

I don't know that I'd have consulted it if I had known about it prior to finishing Binary Witness and Code Runner (stopping to look at maps gets in the way of the reading), but I still like it.