Another book I'd recommend, though on a slightly different subject is COLD ZERO, by a former sniper with the FBI's elite HuRT(Hostage Rescue Team).
The author, Christopher Whitcomb, was a former professional scriptwriter for politicians before deciding to get a proper job and work for a living. His experiance shows; the book is well written, if a little gung ho.
The book includes details of HuRT's very tough Selection and an insider's view of the FBI's most infamous missions: Ruby Ridge and Waco.
Out of print now but you should be able to finda copy on Amazon etc. Well worth a read.
14 Int was indeed part of the DSF set up, the FRU was under control of Director Intelligence. Both played separate roles in NI during those days and the book covers both in some part as 'Rob Lewis' did a bit in both units. Pretty down to earth, normal sort of coverage with no door-kicking, room spraying, abseiling, nonsense.