Michał Płachta started using Scala commercially in 2014 and has been an active contributor to the Scala and JVM communities since. He regularly speaks at conferences, runs workshops, and organizes meetups to help others become better at functional programming. You can find his blog at michalplachta.com.
"""An absolutely wonderful book for someone that has tried and failed to understand functional programming."" William E. Wheeler ""A very practical manuscript."" Ubaldo Pescatore ""Nice introduction to functional programming. Sure to get Java, Javascript, and C# developers into functional programming."" Anjan Bacchu"