There are two important things worth noting about fired FBI Director James Comey’s new tell-all, which is already Amazon’s No. 1 seller.

First, it has almost nothing in the way of real news. No bombshells, almost no dramatic factual revelations. The book, for all intents and purposes, simply repeats his past congressional testimony.

Second, all the headline-grabbing details are either Comey’s petty criticism of President Trump’s tan, height and hand size; unpleasant and deeply personal denigrations of his character; or dishonest or salacious (and unprovable) speculation about the state of his marriage and his sex habits.

The latter, of course, is how you sell books — especially to Trump-haters.

But it’s also — surprisingly, for someone who makes clear he despises the president — a very Trump-like reaction: Someone mistreated you? Start name-calling.

Trump, predictably, reacted in kind, blasting Comey on Twitter (and not entirely without justification) as “a weak and untruthful slime ball.” Which is probably the reaction Comey and his publishers hoped for.

So what’s really going on here? For one thing, Comey is determined to get revenge against Trump for firing him, and by any means necessary. And he wants “redemption” from all the Democrats who believe he cost Hillary Clinton the election by his mishandling of her email probe (even though, he claims, Barack Obama “forgave” him).

But while Comey’s speculation that it’s “possible” a lurid “pee tape” with Russian prostitutes exists will have Trump-haters whinnying with delight, it undermines his own credibility and his cloying pose as a heroic “above-it-all” rock of integrity.

Nor is it helped by another tease: his claim that still-classified information (which, unlike every conversation with Trump, he can’t discuss) would have “cast serious doubt” on then-AG Loretta Lynch’s ability to investigate Clinton.

Bizarrely, he also insists Lynch never “interfered with the conduct of the investigation” — yet complains she ordered him to refer to the probe as simply “a matter,” parroting “the Clinton campaign strategy.”

(Comey, by the way, did exactly as he was told, as he did all through the investigation, because “I didn’t want to make [Hillary] an illegitimate president.”)

The book, in short, is a work of revenge by someone convinced he was badly wronged for trying to save the country from an unworthy president.

Sure, some of his criticism of Trump is doubtless valid. But by diving headfirst into the gutter, he’s done more damage to his own reputation than to the president’s.

In the end, Comey’s “Higher Loyalty” looks to be fully devoted to his own ego.