This may only be of interest to a small niche of readers but you can get a free book on software development peer code review. It's free P&P too. I found it through the Coding Horror website. No idea how long it will be available for or how many are on offer.
You have to enter email and delivery details and they send you a confirmation link.
Apparently it will take at least 15 days to arrive and 5 extra for outside the US.