Zend Framework: Surviving The Deep End was designed for online community review. This means I extort the public into correcting my mistakes so I don't need to go hire lots of proof readers and technical reviewers. Clever tactic, eh?
The comment system is built into the book as an inline system, i.e. you can write comments specific to any paragraph of the entire text by popping open a comment form using the provided links after each paragraph (you can also read existing comments the same way!). The link text itself shows the current number of comment for the preceding paragraph or code block.
General comments will be possible soon, but for now comment to my blog for those. The general end-of-page comments will be implemented soon.
The entire system uses Zend Framework in the backend, with the frontend powered by jQuery. In case you want to credit me for its creation, I should note I stole the idea lock, stock and barrel from two other online books: The Django Book and Real World Haskell. They use similar systems so I merely built the idea along those lines to fit my needs. Kudos to the kids who did this first!
Comments are linked to the specific id of each paragraph which is generated in the Docbook sources I edit and forever immortalised in the XML so that subsequent editing does not alter the id of a paragraph once its set. The id is basically the MD5 hash of the original paragraph text when it was first added.
I hope the system proves useful in adding more atomic comments so everyone can pick apart the whole text and force me to improve on it. Feel free to comment with a vengeance!