Chris Christie’s comeback tour will continue next week with publication of a book, Republican Rescue, in which the former New Jersey governor seeks to present himself as the face of the party after Donald Trump, and a plausible contender for the presidential nomination in 2024.

Such efforts have already seen the one-time presidential candidate clash with Trump, who did not take kindly to Christie warning in a speech in Nevada last weekend: “We can no longer talk about the past and the past elections – no matter where you stand on that issue, no matter where you stand, it is over.”

In a statement, Trump, who is likely to run again in 2024, claimed Christie was “absolutely massacred by his statements that Republicans have to move on from the past, meaning the 2020 election fraud”.

Christie then told Axios, in an interview due to run on Sunday, he was “not going to get into a back-and-forth” with the longtime friend he helped prepare for debates with Joe Biden and who nearly made him White House chief of staff.

But Christie’s book seems guaranteed to anger Trump further. In a copy obtained by the Guardian, Christie writes that Republicans “need to renounce the conspiracy theories and truth deniers, the ones who know better and the ones who are just plain nuts”.

The former governor does not say if he thinks Trump knows better about his claims of electoral fraud, or is one of those who is “nuts”.

But he adds: “We need to give our supporters facts that will help put all these fantasies to rest, so everyone can focus with clear minds on the issues that really matter. We need to quit wasting our time, our energy and our credibility on claims that won’t ever convince anyone or bring fresh converts onboard.”

Condemning the likes of Marjorie Taylor Greene, a hard-right Georgia congresswoman who has expressed support for conspiracy theories, Christie says Trump indulges such figures because he likes “anyone who says nice things about him”.

Discussing the QAnon conspiracy theory, which holds that high-profile Democrats are involved in satanic child abuse, Christie writes that such beliefs “would be ridiculous” if they were not “so sad”.

The FBI considers QAnon a potential terrorist threat. Trump, however, has said its followers share his concern about crime, “love our country” and “like me very much”.

Told last year that QAnon supporters believe he is “secretly saving the world” from a “satanic cult of paedophiles and cannibals”, Trump said: “I haven’t heard that but is that supposed to be a good thing or a bad thing?”

“Many in our society,” Christie writes in Republican Rescue, “use these wild, untrue conspiracy theories to advance their political agendas.”

Christie left office in New Jersey under the cloud of the Bridgegate payback scandal and with historically low approval. Regardless, he continues to tout his pugnacious Jersey persona – a political proposition roundly rejected by Republican voters in the presidential primary in 2016 – writing that “everyone knows I never pull my punches” and “I call things as I see them”.

Some observers, however, question Christie’s sincerity in his stand against Trumpism, given his longstanding closeness to Trump.

Eric Boehlert, author of the Press Run newsletter, wrote critically on Friday about a CNN special, Being Chris Christie, due for broadcast on Monday.

“Today,” Boehlert wrote, “Christie is promoting himself, with the help of CNN, as a brave truth-teller who’s standing up to Trump and his Big Lie about the 2020 election … but Christie may have had the longest delayed conversion to the anti-Trump crowd of any Republican in America.

“Just last year Christie helped Trump prep for a presidential debate. After watching Trump get impeached, Christie still jumped at the chance to be near the center of power to help the maniac get re-elected … Days after helping with Trump’s prep, where everyone was unvaccinated and unmasked, Christie was hospitalised with Covid.”

In his book, Christie describes both his role in Trump’s debate prep and the bout with Covid which sent him to intensive care.

On the debate stage, in Cleveland, Trump notoriously refused to condemn the far-right Proud Boys, instead telling them to “stand back and stand by”.

The New Jersey columnist Charles Stile said then Christie’s defence of Trump’s words “served to remind us of his own trajectory” as a “one-time truth-telling, center-right darling of the GOP [who] embraced his role as a trusted adviser in Trump’s orbit”.

Another Jersey columnist, Alan Steinberg, called Christie “a person of irrepressible ambition, without limits or guard rails … and an essential component of that ambition is an obsessive quest to be relevant”.

Republican Revival will be published on Tuesday.