There's been several pretty decent BATTLESTAR GALACTICA reference works over the last couple of decades* (I wish someone would do something similar for shows like "V" and BUCK ROGERS IN THE 25th CENTURY) but this 1995 tome was the first... and still amongst the best (which is why my copy looks so battered!).
GALACTIC SCI-FI TELEVISION SERIES REVISITED (yuck: clunky title!) is actually a fan-produced (Alpha Control Press) compilation of articles and features that had first appeared across various issues of EPI-LOG and EPI-LOG JOURNAL during the early nineties.
As the basic cover design suggests, this is a pretty lo-fi effort. The interior pages are printed on newsprint grade paper (ironically, EPI-LOG itself had progressed to a rather nice square-bound magazine, with better paper stock, by this point) which does the photos no favours. But it's the text that makes this worth tracking down even today.
It covers the original series and GALACTICA 1980 (including a pulls-no-punches interview with the latter's former Story Editors) in considerable detail. There's still room for the definitive behind-the-scenes book on the show(s), but this comes as close as any.
BG and G80 dominate but there's also substantial coverage of THE INVADERS, THE FANTASTIC JOURNEY and WAR OF THE WORLDS. It's a slightly eccentric mix but I reckon, thanks to the dearth of detailed analysis of any of those shows, this should be a must-have for fans of any one of them.
* I've got them all!