First of all greetings to the authors and thanks for being available for questions.
In the past few years we've seen quite some progress in all Hadoop related projects, including Mahout.
How can the books keep up with the pace of change in the Hadoop ecosystem?
Do you think as Mahout is still heavily under construction and many more features and algorithms yet to come, can we expect a second release of the book later on? Is it in plan to follow the roadmap and release an update of the book too after Mahout reaches certain milestones in the future?
Things are changing fast. Hadoop is an excellent tool for its purpose and is actually getting somewhat mature. It is not an ideal tool for machine learning algorithms. I would not be surprised if some of the other distributed computing frameworks that are emerging, which are designed for a bit more general purpose application, become more popular within a few years for stuff like this. But that's still a few years off at least.
And if that changes, I would not be surprised if Mahout (or another project) changes to reimplement on another framework.
For now I think Mahout has figured out its identity: clustering, classification, collaborative filtering on top of Hadoop. It implements a lot of stuff, and in my opinion has a fair bit of work to do to polish and document what's there. I do not anticipate big changes in what it does, but I do anticipate refinement.
There are no plans for a second edition of the book at this point, as it would be years away at least. The final version of the book is written for Mahout 0.5, which is recent as of a few months ago, and that should remain a useful guide for versions of Mahout for the next 1-2 years.
Please note that the examples from the book are available on-line and we will keep these examples up-to-date with the latest Mahout. Some of the examples are integrated into Mahout so we won't be able to change Mahout too much without updating those.