I regard the original Foundation Trilogy as canonical (silly, but canonical—silly because the author was in his twenties, and also because, well, the whole “golden age” space opera genre was intrinsically silly; canonical because the story arc works better without all the retcon* cruft larded onto the tale in Asimov’s ill-advised series of sequels and prequels commencing three decades later), and actually returned to it a couple of years ago with some nostalgic pleasure. Harmless fun, and I could likely read the three volumes again today in fewer hours than the dramatization would consume. Regarding hours consumed, see the footnote.

cordially,

*Trigger warning: TVTropes link. Potential major timesink. Proceed with caution.