The CRPG Book Project is a collaborative, non-profit effort to create a free, easily available e-book on the history of Computer Role-Playing Games.
I contributed to it by penning a piece on S.T.A.L.K.E.R.: Shadow of Chernobyl, in which I explained the reasons for it being such a fascinating FPS/RPG hybrid that still holds up more than a decade later. The article can be found on Page 362 of the CRPG Book Project. Available for reading via URL below.