There are several scanned books of interest available online:

Sketches of the Royal Irish Constabulary (1886)    http://www.archive.org/details/sketchesroyalir00bropgoog   

The History of the R.I.C. (1871)                            http://www.archive.org/details/historyroyaliri00curtgoog

Road and Route Guide for Ireland of the R.I.C. (1893)  http://www.archive.org/details/deviahiberniaroa00daggrich

Steve