Inside The Third Reich is a good read, but a bit self-serving. Remember, Speer just barely escaped the noose at Nurenburg. (The Russians were adamant upon hanging him, for all of the laborers who died in the armament plants.) And he basically wrote it on TP in Spandau in an effort to justify himself to his kids and to posterity.

Trevor-Roper, though... remember, he's the guy who "authenticated" the Hitler Diary forgeries, so I take that guy with a full shaker of salt.