John Spencer is having Reader Appreciation Week. You can get each of his books for $1 on Kindle. He's changed positions recently but I still think of him as a sixth grade teacher.
There's something for everyone. He's got a book with help for new teachers (Sustainable Start), YA lit (Drawn into Danger), edtech satire (Pencil Me In), and general thoughts on education (Sages and Lunatics & Teaching Unmasked).
For full disclosure, I consider him a friend in the "I've never met him face to face but interact him with online" category that most of my teacher-friends now fall into. However, he didn't ask me to do this and, in fact, wouldn't even consider asking.
Note that you don't actually have to own a Kindle to read them. You can get the apps for your mobile or download the reader software for your desktop or laptop.
(PS - I didn't forget about the assessment overview I promised in The Cycle but I have no idea how I'm going to translate this crazy bubble-flow-mind-timeline chart thing I drew into a blog post)