That's the older edition of the book which covered Redis, Neo4J, CouchDB, MongoDB, HBase, Riak and Postgres. At the time this was published I was already using CouchDB, Redis and PostgreSQL so we bought a (small) crate of these for my new department's employees.

The new edition can be found at https://amzn.to/2KpxOqU and covers Redis, Neo4J, CouchDB, MongoDB, HBase, Postgres, and DynamoDB. I think the most interesting thing about the new edition is that it drops Riak in favor of DynamoDB. They're both K/V stores but trading an open source database for a DBaaS shows me how entrenched the Amazon ecosystem has become in the last 5 years.

Interestingly, one of the authors answers the question of how they chose which databases to cover with "We did have some criteria, if not explicit. The databases had to be open source—we didn’t want to cover any databases that would tie readers to a company." I guess that's not a strong part of the criteria? I guess a database experimenter could still complete the book's exercises using Amazon's free tier?

Its look like publisher has whole series on "Seven X in Seven Weeks"