The 45-year-old, who was sentenced to 30 years last week, says she is close to finishing her manuscript and will release it next month.
In a letter sent from her prison cell in Spain, Smith said the 80,000-word book 'has been one way of passing my time in here'.
She wrote: "I have now finished it and I am confident, with all the attention this case has attracted, I will find a publisher.
"I am determined the truth will come out about what happened. I also want to expose all the dirty tricks which the English and Spanish authorities have deployed to prevent the truth coming out."
But friends of the family are said to be appalled by the idea.
One told the Sunday Mirror: "The idea that Lianne wants to write about the children's murders is abhorrent.
"Her family wish she would just accept her punishment and stop causing so much pain."
Smith was found guilty two weeks ago of murdering daughter Rebecca, five, and son Daniel, 11 months.
The deaths happened a few days after Smith's partner, Martin Smith, was extradited to the UK on charges of sexually abusing her eldest daughter from another relationship.
He was convicted of rape and later hanged himself in prison.
Following his deportation, Smith claimed she thought British social services had arrived in Spain to take her children away from her
She told another psychiatrist she killed them 'out of love' but the prosecution described the murders as 'abominable'.
Smith's lawyer Jenifer Lahoz Abos will lodge an appeal at a higher court claiming she did not receive a fair trial.
"Lianne suffers from psychosis and she needs psychiatric treatment," she said. "She should not be locked up in a regular prison."