Documentation on SolrJ

[Thomas L. Redman]

Hi! I am wanting to do nested facets/Grouping/Expand-Collapse using SolrJ, and 
I can find no API for that. I see I can add a pivot field, I guess to a query 
in general, but that doesn’t seem to work at all, I get an NPE. The 
documentation on SolrJ is sorely lacking, the documentation I have found is 
less than a readme. Are there any books that provided a good tretise on SolrJ 
specifically? Does SolrJ support these more advanced features?