I've written a short chess puzzle eBook which is free on Amazon Kindle all this weekend - do download and enjoy!
Amazon US: http://amzn.to/UNy6BH
Amazon UK: http://amzn.to/Qnfeh8
I'm now writing a longer puzzle eBook for players ~1100-1800 which has reached its funding goal on Kickstarter, but I'm still adding in an extra puzzle for every extra backer before it finishes on Sunday!
If you'd like to have a look at the sort of puzzles in this book, here's a link to the Kickstarter project: