Nice tutorial for getting started with Solr version 5: https://examples.javacodegeeks.com/enterprise-java/apache-solr/apache-solr-tutorial-beginners/
Major changes from Solr version 4 to 5: https://cwiki.apache.org/confluence/display/solr/Major+Changes+from+Solr+4+to+Solr+5
Notable ones:
1) Solr is no longer distributed as a “war” (Web Application Archive) suitable for deployment in any Servlet Container. Solr is now distributed as a stand alone java server application, including start and stop scripts.
2) Changes in bin/solr, bin/post scripts
Major Changes from Solr version 5 to 6: https://cwiki.apache.org/confluence/display/solr/Major+Changes+from+Solr+5+to+Solr+6
This quora answer has good links for learning Solr: https://www.quora.com/What-is-the-best-way-to-learn-SOLR
