Besides the handbooks already recommended, I can only agree that you search on the following authors:
Monika M. Müller
Reinhardt M. Kristensen
Alexander B. Tzetlin
Reinhardt M. Rieger
Claude Jouin or Jouin-Toulmond
Nathan W. Riser
There are off course many more, but these will give you a good start.
I made a review of interstitial polychaetes in 2005 that can lead you to much of the general litterature:
Worsaae K & Kristensen RM, 2005. Evolution of interstitial polychaetes. Hydrobiologia 535/536: 319-340.
As well as revisions of Nerillidae and Psammodrilidae, that will give you the litterature on these particular families:
Worsaae K, 2005. Systematics of Nerillidae (Polychaeta, Annelida). Meiofauna Marina 14: 49-74.
Worsaae K & Sterrer, W (2006). Description of two new interstitial species of Psammodrilidae (Annelida) from Bermuda. Marine Biology Research 2: 431-445.
Ass. Prof. Katrine Worsaae
Marine Biological Laboratory, Elsinore
Email: kworsaae At snm.ku.dk (will soon be changed to kworsaae At bi.ku.dk)