What is the author's style in Prelude to Foundation by Isaac Asimov?

A wholly anonymous storyteller of Prelude to Foundation follows with considerable sympathy and empathy the adventures of mathematician Hari Seldon and historian/bodyguard Dors Venabili during their "flight" from the Emperor's ostensibly evil and manipulative chief of staff, Eto Demerzel. Prelude to Foundation is told in the third person past tense, largely through narrative connecting extensive dialog, without delving into the characters' inner thought processes. There are indications that the storytelling is as much as twenty years after-the-fact (based on a comment that Emperor Cleon I is the last of his dynasty to sit on the Imperial throne). It also acknowledges that the Hari Seldon who appears here is a far cry from the white-haired, wheelchair-bound cultural icon he is destined to become.

Apart from that one reference, the narrator is far from a hagiographer. All of the well-rounded characters have flaws, the hapless protagonist in particular. Asimov introduces his characters quite naturally and builds detail about them and interactions between and among them gradually, releasing hints to what is actually going on far too subtly to be detected until the final reckoning, which is filled with "aha" moments. A second reading, knowing the outcome would, doubtless, be rewarding. Prelude to Foundation makes reading and appreciating Asimov's classic Foundation trilogy easier.