Hi Kevin,
I downloaded the version of the User Guide in this thread and did some basic updates. I changed versions to 0.9.7, corrected a few typos I found and added both sets of building on Linux HTML docs as new chapters. I changed the TOC to reflect the new additions.
What I DIDN'T do is update the all-important Validation section or add details about plugins. I'm not all that au fait with them yet.
I didn't mention myself anywhere except as a contributor in the ePub's metadata. I hope that is OK.
Even so, I hope my contribution is a step forward.